diff --git a/aleksis/apps/alsijil/locale/ar/LC_MESSAGES/django.po b/aleksis/apps/alsijil/locale/ar/LC_MESSAGES/django.po
index cc86fc5cf3595ae437aef2bd28e649204b1af4ff..a98f11e58e851ea9d34f885b57c0be53c9f646a9 100644
--- a/aleksis/apps/alsijil/locale/ar/LC_MESSAGES/django.po
+++ b/aleksis/apps/alsijil/locale/ar/LC_MESSAGES/django.po
@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2020-12-05 21:26+0100\n"
+"POT-Creation-Date: 2021-01-22 22:01+0100\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -18,11 +18,63 @@ msgstr ""
 "Content-Transfer-Encoding: 8bit\n"
 "Plural-Forms: nplurals=6; plural=n==0 ? 0 : n==1 ? 1 : n==2 ? 2 : n%100>=3 && n%100<=10 ? 3 : n%100>=11 && n%100<=99 ? 4 : 5;\n"
 
+#: data_checks.py:15
+msgid "Delete object"
+msgstr ""
+
+#: data_checks.py:25
+msgid "Set current groups"
+msgstr ""
+
+#: data_checks.py:36
+msgid "Reset personal note to defaults"
+msgstr ""
+
+#: data_checks.py:48
+msgid "Ensure that there are no personal notes in cancelled lessons"
+msgstr ""
+
+#: data_checks.py:49
+msgid "The personal note is related to a cancelled lesson."
+msgstr ""
+
+#: data_checks.py:72
+msgid "Ensure that 'groups_of_person' is set for every personal note"
+msgstr ""
+
+#: data_checks.py:73
+msgid "The personal note has no group in 'groups_of_person'."
+msgstr ""
+
+#: data_checks.py:107
+msgid "Ensure that there are no filled out lesson documentations on holidays"
+msgstr ""
+
+#: data_checks.py:108
+msgid "The lesson documentation is on holidays."
+msgstr ""
+
+#: data_checks.py:143
+msgid "Ensure that there are no filled out personal notes on holidays"
+msgstr ""
+
+#: data_checks.py:144
+msgid "The personal note is on holidays."
+msgstr ""
+
+#: data_checks.py:174
+msgid "Ensure that there are no excused personal notes without an absence"
+msgstr ""
+
+#: data_checks.py:175
+msgid "The personal note is marked as excused, but not as absent."
+msgstr ""
+
 #: forms.py:29
 msgid "Homework for the next lesson"
 msgstr ""
 
-#: forms.py:54 templates/alsijil/class_register/week_view.html:168
+#: forms.py:54 templates/alsijil/class_register/week_view.html:191
 #: templates/alsijil/print/full_register.html:199
 msgid "Group"
 msgstr ""
@@ -53,16 +105,16 @@ msgid "End period"
 msgstr ""
 
 #: forms.py:130 templates/alsijil/absences/register_confirm.html:52
-#: templates/alsijil/class_register/lesson.html:243
+#: templates/alsijil/class_register/lesson.html:247
 #: templates/alsijil/class_register/person.html:207
-#: templates/alsijil/class_register/week_view.html:261
+#: templates/alsijil/class_register/week_view.html:287
 #: templates/alsijil/print/full_register.html:75
 #: templates/alsijil/print/full_register.html:312
 msgid "Absent"
 msgstr ""
 
 #: forms.py:131 templates/alsijil/absences/register_confirm.html:56
-#: templates/alsijil/class_register/lesson.html:245
+#: templates/alsijil/class_register/lesson.html:249
 #: templates/alsijil/class_register/person.html:98
 #: templates/alsijil/class_register/person.html:215
 #: templates/alsijil/partials/mark_as_buttons.html:2
@@ -73,14 +125,14 @@ msgstr ""
 msgid "Excused"
 msgstr ""
 
-#: forms.py:133 models.py:37 models.py:64
-#: templates/alsijil/class_register/lesson.html:246
-#: templates/alsijil/class_register/lesson.html:281
+#: forms.py:133 models.py:45 models.py:79
+#: templates/alsijil/class_register/lesson.html:250
+#: templates/alsijil/class_register/lesson.html:285
 msgid "Excuse type"
 msgstr ""
 
-#: forms.py:138 templates/alsijil/class_register/lesson.html:248
-#: templates/alsijil/class_register/lesson.html:302
+#: forms.py:138 templates/alsijil/class_register/lesson.html:252
+#: templates/alsijil/class_register/lesson.html:306
 #: templates/alsijil/print/full_register.html:314
 msgid "Remarks"
 msgstr ""
@@ -111,14 +163,14 @@ msgstr ""
 msgid "My students"
 msgstr ""
 
-#: menus.py:71 models.py:38 templates/alsijil/excuse_type/list.html:8
+#: menus.py:71 models.py:46 templates/alsijil/excuse_type/list.html:8
 #: templates/alsijil/excuse_type/list.html:9
 #: templates/alsijil/partials/legend.html:26
 msgid "Excuse types"
 msgstr ""
 
-#: menus.py:82 models.py:70 models.py:201
-#: templates/alsijil/class_register/lesson.html:247
+#: menus.py:82 models.py:84 models.py:232
+#: templates/alsijil/class_register/lesson.html:251
 #: templates/alsijil/extra_mark/list.html:8
 #: templates/alsijil/extra_mark/list.html:9
 #: templates/alsijil/partials/legend.html:41
@@ -163,75 +215,75 @@ msgstr ""
 msgid "Can register an absence for a person"
 msgstr ""
 
-#: models.py:25 models.py:188
+#: models.py:33 models.py:219
 msgid "Short name"
 msgstr ""
 
-#: models.py:26 models.py:189 templates/alsijil/class_register/groups.html:20
+#: models.py:34 models.py:220 templates/alsijil/class_register/groups.html:20
 #: templates/alsijil/partials/persons_with_stats.html:14
 #: templates/alsijil/partials/persons_with_stats.html:24
 msgid "Name"
 msgstr ""
 
-#: models.py:54 models.py:121
+#: models.py:69 models.py:144
 msgid "Year"
 msgstr ""
 
-#: models.py:101
+#: models.py:122
 msgid "Personal note"
 msgstr ""
 
-#: models.py:102 templates/alsijil/class_register/lesson.html:101
-#: templates/alsijil/class_register/lesson.html:233
-#: templates/alsijil/class_register/week_view.html:68
-#: templates/alsijil/class_register/week_view.html:242
+#: models.py:123 templates/alsijil/class_register/lesson.html:105
+#: templates/alsijil/class_register/lesson.html:237
+#: templates/alsijil/class_register/week_view.html:71
+#: templates/alsijil/class_register/week_view.html:267
 msgid "Personal notes"
 msgstr ""
 
-#: models.py:127 templates/alsijil/class_register/lesson.html:129
-#: templates/alsijil/class_register/week_view.html:90
-#: templates/alsijil/class_register/week_view.html:177
-#: templates/alsijil/print/full_register.html:371
+#: models.py:150 templates/alsijil/class_register/lesson.html:133
+#: templates/alsijil/class_register/week_view.html:106
+#: templates/alsijil/class_register/week_view.html:200
+#: templates/alsijil/print/full_register.html:369
 msgid "Lesson topic"
 msgstr ""
 
-#: models.py:128 templates/alsijil/class_register/lesson.html:137
-#: templates/alsijil/class_register/week_view.html:91
-#: templates/alsijil/class_register/week_view.html:183
-#: templates/alsijil/class_register/week_view.html:216
-#: templates/alsijil/print/full_register.html:372
+#: models.py:151 templates/alsijil/class_register/lesson.html:141
+#: templates/alsijil/class_register/week_view.html:107
+#: templates/alsijil/class_register/week_view.html:206
+#: templates/alsijil/class_register/week_view.html:239
+#: templates/alsijil/print/full_register.html:370
 msgid "Homework"
 msgstr ""
 
-#: models.py:129 templates/alsijil/class_register/lesson.html:145
-#: templates/alsijil/class_register/week_view.html:92
-#: templates/alsijil/class_register/week_view.html:189
-#: templates/alsijil/class_register/week_view.html:222
+#: models.py:152 templates/alsijil/class_register/lesson.html:149
+#: templates/alsijil/class_register/week_view.html:108
+#: templates/alsijil/class_register/week_view.html:212
+#: templates/alsijil/class_register/week_view.html:245
 msgid "Group note"
 msgstr ""
 
-#: models.py:171 templates/alsijil/class_register/lesson.html:97
-#: templates/alsijil/class_register/lesson.html:120
+#: models.py:202 templates/alsijil/class_register/lesson.html:101
+#: templates/alsijil/class_register/lesson.html:124
 msgid "Lesson documentation"
 msgstr ""
 
-#: models.py:172 templates/alsijil/class_register/week_view.html:67
+#: models.py:203 templates/alsijil/class_register/week_view.html:68
 msgid "Lesson documentations"
 msgstr ""
 
-#: models.py:200
+#: models.py:231
 msgid "Extra mark"
 msgstr ""
 
-#: models.py:208
+#: models.py:239
 msgid "Can view week overview"
 msgstr ""
 
-#: models.py:209
+#: models.py:240
 msgid "Can register absence"
 msgstr ""
 
-#: models.py:210
+#: models.py:241
 msgid "Can list all personal note filters"
 msgstr ""
 
@@ -263,6 +315,10 @@ msgstr ""
 msgid "Lessons in the past are not affected by this setting, you can open them whenever you want."
 msgstr ""
 
+#: preferences.py:68
+msgid "Allow teachers to add data for lessons in holidays"
+msgstr ""
+
 #: tables.py:16 tables.py:36
 msgid "Edit"
 msgstr ""
@@ -274,13 +330,13 @@ msgstr ""
 #: templates/alsijil/absences/register.html:5
 #: templates/alsijil/absences/register.html:6
 #: templates/alsijil/class_register/person.html:30
-#: templates/alsijil/class_register/week_view.html:256
+#: templates/alsijil/class_register/week_view.html:282
 #: templates/alsijil/partials/persons_with_stats.html:115
 msgid "Register absence"
 msgstr ""
 
 #: templates/alsijil/absences/register.html:9
-#: templates/alsijil/class_register/lesson.html:242
+#: templates/alsijil/class_register/lesson.html:246
 msgid "Person"
 msgstr ""
 
@@ -382,13 +438,12 @@ msgid "My next lesson"
 msgstr ""
 
 #: templates/alsijil/class_register/lesson.html:46
-#: templates/alsijil/class_register/lesson.html:167
+#: templates/alsijil/class_register/lesson.html:171
 #, python-format
 msgid "%(period)s. period"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:77
-#: templates/alsijil/class_register/lesson.html:359
+#: templates/alsijil/class_register/lesson.html:79
 #, python-format
 msgid ""
 "\n"
@@ -396,8 +451,7 @@ msgid ""
 "        "
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:85
-#: templates/alsijil/class_register/lesson.html:367
+#: templates/alsijil/class_register/lesson.html:87
 #, python-format
 msgid ""
 "\n"
@@ -405,40 +459,40 @@ msgid ""
 "        "
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:107
+#: templates/alsijil/class_register/lesson.html:111
 msgid "Previous lesson"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:111
-#: templates/alsijil/class_register/lesson.html:342
+#: templates/alsijil/class_register/lesson.html:115
+#: templates/alsijil/class_register/lesson.html:346
 msgid "Change history"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:166
+#: templates/alsijil/class_register/lesson.html:170
 msgid "Overview: Previous lesson"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:173
+#: templates/alsijil/class_register/lesson.html:177
 msgid "Lesson topic of previous lesson:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:180
+#: templates/alsijil/class_register/lesson.html:184
 msgid "Homework for this lesson:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:187
+#: templates/alsijil/class_register/lesson.html:191
 msgid "Group notes for previous lesson:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:194
+#: templates/alsijil/class_register/lesson.html:198
 msgid "Absent persons:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:201
+#: templates/alsijil/class_register/lesson.html:205
 msgid "Late persons:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:244
+#: templates/alsijil/class_register/lesson.html:248
 #: templates/alsijil/class_register/person.html:110
 #: templates/alsijil/partials/persons_with_stats.html:17
 #: templates/alsijil/partials/persons_with_stats.html:34
@@ -447,10 +501,33 @@ msgstr ""
 msgid "Tardiness"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:267
+#: templates/alsijil/class_register/lesson.html:271
 msgid "Tardiness (in m)"
 msgstr ""
 
+#: templates/alsijil/class_register/lesson.html:364
+#, python-format
+msgid ""
+"\n"
+"            Previous %(subject)s lesson\n"
+"          "
+msgstr ""
+
+#: templates/alsijil/class_register/lesson.html:372
+#, python-format
+msgid ""
+"\n"
+"            Next %(subject)s lesson\n"
+"          "
+msgstr ""
+
+#: templates/alsijil/class_register/lesson.html:387
+msgid ""
+"\n"
+"                This lesson overlaps with holidays and can't be edited.\n"
+"              "
+msgstr ""
+
 #: templates/alsijil/class_register/person.html:8
 msgid "Class register: person"
 msgstr ""
@@ -555,44 +632,44 @@ msgid ""
 "      %(instance)s"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:84
+#: templates/alsijil/class_register/week_view.html:100
 msgid "Period"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:86
+#: templates/alsijil/class_register/week_view.html:102
 msgid "Groups"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:88
-#: templates/alsijil/class_register/week_view.html:163
+#: templates/alsijil/class_register/week_view.html:104
+#: templates/alsijil/class_register/week_view.html:186
 #: templates/alsijil/print/full_register.html:169
 #: templates/alsijil/print/full_register.html:200
 msgid "Subject"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:89
-#: templates/alsijil/class_register/week_view.html:173
+#: templates/alsijil/class_register/week_view.html:105
+#: templates/alsijil/class_register/week_view.html:196
 msgid "Teachers"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:262
+#: templates/alsijil/class_register/week_view.html:288
 msgid "unexcused"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:265
+#: templates/alsijil/class_register/week_view.html:291
 msgid "Summed up tardiness"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:268
+#: templates/alsijil/class_register/week_view.html:294
 #: templates/alsijil/partials/persons_with_stats.html:94
 msgid "Count of tardiness"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:297
+#: templates/alsijil/class_register/week_view.html:323
 msgid "No lessons available"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:300
+#: templates/alsijil/class_register/week_view.html:326
 msgid ""
 "\n"
 "            There are no lessons for the selected group or teacher in this week.\n"
@@ -661,7 +738,7 @@ msgid "Data complete"
 msgstr ""
 
 #: templates/alsijil/partials/lesson_status_icon.html:12
-#: templates/alsijil/print/full_register.html:406
+#: templates/alsijil/print/full_register.html:404
 msgid "Lesson cancelled"
 msgstr ""
 
@@ -678,9 +755,9 @@ msgid "Substitution"
 msgstr ""
 
 #: templates/alsijil/partials/mark_as_buttons.html:4
-#: templates/alsijil/print/full_register.html:335
-#: templates/alsijil/print/full_register.html:424
-#: templates/alsijil/print/full_register.html:439
+#: templates/alsijil/print/full_register.html:334
+#: templates/alsijil/print/full_register.html:422
+#: templates/alsijil/print/full_register.html:437
 msgid "e"
 msgstr ""
 
@@ -836,17 +913,17 @@ msgid "Date"
 msgstr ""
 
 #: templates/alsijil/print/full_register.html:309
-#: templates/alsijil/print/full_register.html:369
+#: templates/alsijil/print/full_register.html:367
 msgid "Pe."
 msgstr ""
 
 #: templates/alsijil/print/full_register.html:310
-#: templates/alsijil/print/full_register.html:370
+#: templates/alsijil/print/full_register.html:368
 msgid "Subj."
 msgstr ""
 
 #: templates/alsijil/print/full_register.html:311
-#: templates/alsijil/print/full_register.html:374
+#: templates/alsijil/print/full_register.html:372
 msgid "Te."
 msgstr ""
 
@@ -854,70 +931,70 @@ msgstr ""
 msgid "Tard."
 msgstr ""
 
-#: templates/alsijil/print/full_register.html:330
+#: templates/alsijil/print/full_register.html:329
 msgid "Yes"
 msgstr ""
 
-#: templates/alsijil/print/full_register.html:363
+#: templates/alsijil/print/full_register.html:361
 msgid "Lesson documentation for week"
 msgstr ""
 
-#: templates/alsijil/print/full_register.html:373
+#: templates/alsijil/print/full_register.html:371
 msgid "Notes"
 msgstr ""
 
-#: views.py:65
+#: views.py:68
 msgid "You either selected an invalid lesson or there is currently no lesson in progress."
 msgstr ""
 
-#: views.py:90
+#: views.py:93
 msgid "You are not allowed to create a lesson documentation for a lesson in the future."
 msgstr ""
 
-#: views.py:127
+#: views.py:141
 msgid "The lesson documentation has been saved."
 msgstr ""
 
-#: views.py:151
+#: views.py:165
 msgid "The personal notes have been saved."
 msgstr ""
 
-#: views.py:570
+#: views.py:591
 msgid "The absences have been marked as excused."
 msgstr ""
 
-#: views.py:585
+#: views.py:606
 msgid "The absence has been marked as excused."
 msgstr ""
 
-#: views.py:721
+#: views.py:749
 msgid "The absence has been saved."
 msgstr ""
 
-#: views.py:741
+#: views.py:770
 msgid "The personal note has been deleted."
 msgstr ""
 
-#: views.py:762
+#: views.py:792
 msgid "The extra mark has been created."
 msgstr ""
 
-#: views.py:773
+#: views.py:804
 msgid "The extra mark has been saved."
 msgstr ""
 
-#: views.py:783
+#: views.py:815
 msgid "The extra mark has been deleted."
 msgstr ""
 
-#: views.py:803
+#: views.py:836
 msgid "The excuse type has been created."
 msgstr ""
 
-#: views.py:814
+#: views.py:848
 msgid "The excuse type has been saved."
 msgstr ""
 
-#: views.py:824
+#: views.py:859
 msgid "The excuse type has been deleted."
 msgstr ""
diff --git a/aleksis/apps/alsijil/locale/de_DE/LC_MESSAGES/django.po b/aleksis/apps/alsijil/locale/de_DE/LC_MESSAGES/django.po
index add03b74eeb7a5e69c3c19dce2a7bedb2038c90d..8ae0b4c53de475658f40a806d3000498c4e1d156 100644
--- a/aleksis/apps/alsijil/locale/de_DE/LC_MESSAGES/django.po
+++ b/aleksis/apps/alsijil/locale/de_DE/LC_MESSAGES/django.po
@@ -7,11 +7,10 @@ msgid ""
 msgstr ""
 "Project-Id-Version: \n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2020-12-05 21:26+0100\n"
+"POT-Creation-Date: 2021-01-22 22:01+0100\n"
 "PO-Revision-Date: 2020-12-05 20:56+0000\n"
 "Last-Translator: Jonathan Weth <teckids@jonathanweth.de>\n"
-"Language-Team: German <https://translate.edugit.org/projects/aleksis/"
-"aleksis-app-alsijil/de/>\n"
+"Language-Team: German <https://translate.edugit.org/projects/aleksis/aleksis-app-alsijil/de/>\n"
 "Language: de_DE\n"
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=UTF-8\n"
@@ -19,11 +18,79 @@ msgstr ""
 "Plural-Forms: nplurals=2; plural=n != 1;\n"
 "X-Generator: Weblate 4.3.2\n"
 
+#: data_checks.py:15
+#, fuzzy
+#| msgid "Delete note"
+msgid "Delete object"
+msgstr "Notiz löschen"
+
+#: data_checks.py:25
+#, fuzzy
+#| msgid "Students list: %(group)s"
+msgid "Set current groups"
+msgstr "Schüler*innenliste: %(group)s"
+
+#: data_checks.py:36
+#, fuzzy
+#| msgid "Relevant personal notes"
+msgid "Reset personal note to defaults"
+msgstr "Relevante persönliche Notizen"
+
+#: data_checks.py:48
+#, fuzzy
+#| msgid "Block adding personal notes for cancelled lessons"
+msgid "Ensure that there are no personal notes in cancelled lessons"
+msgstr "Blockiere das Hinzufügen von persönlichen Notizen für ausgefallene Stunden"
+
+#: data_checks.py:49
+#, fuzzy
+#| msgid "Block adding personal notes for cancelled lessons"
+msgid "The personal note is related to a cancelled lesson."
+msgstr "Blockiere das Hinzufügen von persönlichen Notizen für ausgefallene Stunden"
+
+#: data_checks.py:72
+msgid "Ensure that 'groups_of_person' is set for every personal note"
+msgstr ""
+
+#: data_checks.py:73
+msgid "The personal note has no group in 'groups_of_person'."
+msgstr ""
+
+#: data_checks.py:107
+msgid "Ensure that there are no filled out lesson documentations on holidays"
+msgstr ""
+
+#: data_checks.py:108
+#, fuzzy
+#| msgid "The lesson documentation has been saved."
+msgid "The lesson documentation is on holidays."
+msgstr "Die Stunden-Dokumentation wurde gespeichert."
+
+#: data_checks.py:143
+msgid "Ensure that there are no filled out personal notes on holidays"
+msgstr ""
+
+#: data_checks.py:144
+#, fuzzy
+#| msgid "The personal note has been deleted."
+msgid "The personal note is on holidays."
+msgstr "Die persönliche Notiz wurde gelöscht."
+
+#: data_checks.py:174
+msgid "Ensure that there are no excused personal notes without an absence"
+msgstr ""
+
+#: data_checks.py:175
+#, fuzzy
+#| msgid "The personal notes have been saved."
+msgid "The personal note is marked as excused, but not as absent."
+msgstr "Die persönlichen Notizen wurden gespeichert."
+
 #: forms.py:29
 msgid "Homework for the next lesson"
 msgstr "Hausaufgabe zur nächsten Stunde"
 
-#: forms.py:54 templates/alsijil/class_register/week_view.html:168
+#: forms.py:54 templates/alsijil/class_register/week_view.html:191
 #: templates/alsijil/print/full_register.html:199
 msgid "Group"
 msgstr "Gruppe"
@@ -54,16 +121,16 @@ msgid "End period"
 msgstr "Endstunde"
 
 #: forms.py:130 templates/alsijil/absences/register_confirm.html:52
-#: templates/alsijil/class_register/lesson.html:243
+#: templates/alsijil/class_register/lesson.html:247
 #: templates/alsijil/class_register/person.html:207
-#: templates/alsijil/class_register/week_view.html:261
+#: templates/alsijil/class_register/week_view.html:287
 #: templates/alsijil/print/full_register.html:75
 #: templates/alsijil/print/full_register.html:312
 msgid "Absent"
 msgstr "Abwesend"
 
 #: forms.py:131 templates/alsijil/absences/register_confirm.html:56
-#: templates/alsijil/class_register/lesson.html:245
+#: templates/alsijil/class_register/lesson.html:249
 #: templates/alsijil/class_register/person.html:98
 #: templates/alsijil/class_register/person.html:215
 #: templates/alsijil/partials/mark_as_buttons.html:2
@@ -74,14 +141,14 @@ msgstr "Abwesend"
 msgid "Excused"
 msgstr "Entschuldigt"
 
-#: forms.py:133 models.py:37 models.py:64
-#: templates/alsijil/class_register/lesson.html:246
-#: templates/alsijil/class_register/lesson.html:281
+#: forms.py:133 models.py:45 models.py:79
+#: templates/alsijil/class_register/lesson.html:250
+#: templates/alsijil/class_register/lesson.html:285
 msgid "Excuse type"
 msgstr "Entschuldigungsart"
 
-#: forms.py:138 templates/alsijil/class_register/lesson.html:248
-#: templates/alsijil/class_register/lesson.html:302
+#: forms.py:138 templates/alsijil/class_register/lesson.html:252
+#: templates/alsijil/class_register/lesson.html:306
 #: templates/alsijil/print/full_register.html:314
 msgid "Remarks"
 msgstr "Bemerkungen"
@@ -112,14 +179,14 @@ msgstr "Meine Ãœbersicht"
 msgid "My students"
 msgstr "Meine Schüler*innen"
 
-#: menus.py:71 models.py:38 templates/alsijil/excuse_type/list.html:8
+#: menus.py:71 models.py:46 templates/alsijil/excuse_type/list.html:8
 #: templates/alsijil/excuse_type/list.html:9
 #: templates/alsijil/partials/legend.html:26
 msgid "Excuse types"
 msgstr "Entschuldigungsarten"
 
-#: menus.py:82 models.py:70 models.py:201
-#: templates/alsijil/class_register/lesson.html:247
+#: menus.py:82 models.py:84 models.py:232
+#: templates/alsijil/class_register/lesson.html:251
 #: templates/alsijil/extra_mark/list.html:8
 #: templates/alsijil/extra_mark/list.html:9
 #: templates/alsijil/partials/legend.html:41
@@ -164,75 +231,75 @@ msgstr "Kann eine Absenz für alle Mitglieder eine Gruppe registrieren"
 msgid "Can register an absence for a person"
 msgstr "Kann eine Absenz für eine Person registrieren"
 
-#: models.py:25 models.py:188
+#: models.py:33 models.py:219
 msgid "Short name"
 msgstr "Kurzname"
 
-#: models.py:26 models.py:189 templates/alsijil/class_register/groups.html:20
+#: models.py:34 models.py:220 templates/alsijil/class_register/groups.html:20
 #: templates/alsijil/partials/persons_with_stats.html:14
 #: templates/alsijil/partials/persons_with_stats.html:24
 msgid "Name"
 msgstr "Name"
 
-#: models.py:54 models.py:121
+#: models.py:69 models.py:144
 msgid "Year"
 msgstr "Jahr"
 
-#: models.py:101
+#: models.py:122
 msgid "Personal note"
 msgstr "Persönliche Notiz"
 
-#: models.py:102 templates/alsijil/class_register/lesson.html:101
-#: templates/alsijil/class_register/lesson.html:233
-#: templates/alsijil/class_register/week_view.html:68
-#: templates/alsijil/class_register/week_view.html:242
+#: models.py:123 templates/alsijil/class_register/lesson.html:105
+#: templates/alsijil/class_register/lesson.html:237
+#: templates/alsijil/class_register/week_view.html:71
+#: templates/alsijil/class_register/week_view.html:267
 msgid "Personal notes"
 msgstr "Persönliche Notizen"
 
-#: models.py:127 templates/alsijil/class_register/lesson.html:129
-#: templates/alsijil/class_register/week_view.html:90
-#: templates/alsijil/class_register/week_view.html:177
-#: templates/alsijil/print/full_register.html:371
+#: models.py:150 templates/alsijil/class_register/lesson.html:133
+#: templates/alsijil/class_register/week_view.html:106
+#: templates/alsijil/class_register/week_view.html:200
+#: templates/alsijil/print/full_register.html:369
 msgid "Lesson topic"
 msgstr "Stundenthema"
 
-#: models.py:128 templates/alsijil/class_register/lesson.html:137
-#: templates/alsijil/class_register/week_view.html:91
-#: templates/alsijil/class_register/week_view.html:183
-#: templates/alsijil/class_register/week_view.html:216
-#: templates/alsijil/print/full_register.html:372
+#: models.py:151 templates/alsijil/class_register/lesson.html:141
+#: templates/alsijil/class_register/week_view.html:107
+#: templates/alsijil/class_register/week_view.html:206
+#: templates/alsijil/class_register/week_view.html:239
+#: templates/alsijil/print/full_register.html:370
 msgid "Homework"
 msgstr "Hausaufgaben"
 
-#: models.py:129 templates/alsijil/class_register/lesson.html:145
-#: templates/alsijil/class_register/week_view.html:92
-#: templates/alsijil/class_register/week_view.html:189
-#: templates/alsijil/class_register/week_view.html:222
+#: models.py:152 templates/alsijil/class_register/lesson.html:149
+#: templates/alsijil/class_register/week_view.html:108
+#: templates/alsijil/class_register/week_view.html:212
+#: templates/alsijil/class_register/week_view.html:245
 msgid "Group note"
 msgstr "Gruppennotiz"
 
-#: models.py:171 templates/alsijil/class_register/lesson.html:97
-#: templates/alsijil/class_register/lesson.html:120
+#: models.py:202 templates/alsijil/class_register/lesson.html:101
+#: templates/alsijil/class_register/lesson.html:124
 msgid "Lesson documentation"
 msgstr "Stunden-Dokumentation"
 
-#: models.py:172 templates/alsijil/class_register/week_view.html:67
+#: models.py:203 templates/alsijil/class_register/week_view.html:68
 msgid "Lesson documentations"
 msgstr "Stunden-Dokumentationen"
 
-#: models.py:200
+#: models.py:231
 msgid "Extra mark"
 msgstr "Zusätzliche Markierung"
 
-#: models.py:208
+#: models.py:239
 msgid "Can view week overview"
 msgstr "Kann die Wochenübersicht sehen"
 
-#: models.py:209
+#: models.py:240
 msgid "Can register absence"
 msgstr "Kann eine Absenz registrieren"
 
-#: models.py:210
+#: models.py:241
 msgid "Can list all personal note filters"
 msgstr "Kann alle Filter für persönliche Notizen anzeigen"
 
@@ -264,6 +331,12 @@ msgstr "Erlaube Lehrkräften, Unterrichtsstunden bereits am gleichen Tag und nic
 msgid "Lessons in the past are not affected by this setting, you can open them whenever you want."
 msgstr "Unterrichtsstunden in der Vergangenheit werden nicht durch diese Einstellung beeinflusst, sie können immer geöffnet werden."
 
+#: preferences.py:68
+#, fuzzy
+#| msgid "Teachers and lessons in child groups"
+msgid "Allow teachers to add data for lessons in holidays"
+msgstr "Lehrkräfte und Fächer von Untergruppen"
+
 #: tables.py:16 tables.py:36
 msgid "Edit"
 msgstr "Bearbeiten"
@@ -275,13 +348,13 @@ msgstr "Löschen"
 #: templates/alsijil/absences/register.html:5
 #: templates/alsijil/absences/register.html:6
 #: templates/alsijil/class_register/person.html:30
-#: templates/alsijil/class_register/week_view.html:256
+#: templates/alsijil/class_register/week_view.html:282
 #: templates/alsijil/partials/persons_with_stats.html:115
 msgid "Register absence"
 msgstr "Abwesenheit eintragen"
 
 #: templates/alsijil/absences/register.html:9
-#: templates/alsijil/class_register/lesson.html:242
+#: templates/alsijil/class_register/lesson.html:246
 msgid "Person"
 msgstr "Person"
 
@@ -324,8 +397,7 @@ msgid ""
 "                "
 msgstr ""
 "\n"
-"                  Es gibt keine betroffenen Stunden. Das Eintragen dieser "
-"Abwesenheit wird keinen Effekt haben.\n"
+"                  Es gibt keine betroffenen Stunden. Das Eintragen dieser Abwesenheit wird keinen Effekt haben.\n"
 "                "
 
 #: templates/alsijil/absences/register_confirm.html:59
@@ -394,13 +466,12 @@ msgid "My next lesson"
 msgstr "Meine nächste Stunde"
 
 #: templates/alsijil/class_register/lesson.html:46
-#: templates/alsijil/class_register/lesson.html:167
+#: templates/alsijil/class_register/lesson.html:171
 #, python-format
 msgid "%(period)s. period"
 msgstr "%(period)s. Stunde"
 
-#: templates/alsijil/class_register/lesson.html:77
-#: templates/alsijil/class_register/lesson.html:359
+#: templates/alsijil/class_register/lesson.html:79
 #, python-format
 msgid ""
 "\n"
@@ -411,8 +482,7 @@ msgstr ""
 "          Vorherige %(subject)s Stunde\n"
 "        "
 
-#: templates/alsijil/class_register/lesson.html:85
-#: templates/alsijil/class_register/lesson.html:367
+#: templates/alsijil/class_register/lesson.html:87
 #, python-format
 msgid ""
 "\n"
@@ -423,40 +493,40 @@ msgstr ""
 "          Nächste %(subject)s Stunde\n"
 "        "
 
-#: templates/alsijil/class_register/lesson.html:107
+#: templates/alsijil/class_register/lesson.html:111
 msgid "Previous lesson"
 msgstr "Vorherige Unterrichtsstunde"
 
-#: templates/alsijil/class_register/lesson.html:111
-#: templates/alsijil/class_register/lesson.html:342
+#: templates/alsijil/class_register/lesson.html:115
+#: templates/alsijil/class_register/lesson.html:346
 msgid "Change history"
 msgstr "Veränderungen"
 
-#: templates/alsijil/class_register/lesson.html:166
+#: templates/alsijil/class_register/lesson.html:170
 msgid "Overview: Previous lesson"
 msgstr "Ãœbersicht: Vorherige Stunde"
 
-#: templates/alsijil/class_register/lesson.html:173
+#: templates/alsijil/class_register/lesson.html:177
 msgid "Lesson topic of previous lesson:"
 msgstr "Stundenthema der vorherigen Stunde:"
 
-#: templates/alsijil/class_register/lesson.html:180
+#: templates/alsijil/class_register/lesson.html:184
 msgid "Homework for this lesson:"
 msgstr "Hausaufgaben zu dieser Stunde:"
 
-#: templates/alsijil/class_register/lesson.html:187
+#: templates/alsijil/class_register/lesson.html:191
 msgid "Group notes for previous lesson:"
 msgstr "Gruppennotizen für die vorherige Stunde:"
 
-#: templates/alsijil/class_register/lesson.html:194
+#: templates/alsijil/class_register/lesson.html:198
 msgid "Absent persons:"
 msgstr "Abwesende Personen:"
 
-#: templates/alsijil/class_register/lesson.html:201
+#: templates/alsijil/class_register/lesson.html:205
 msgid "Late persons:"
 msgstr "Verspätete Personen:"
 
-#: templates/alsijil/class_register/lesson.html:244
+#: templates/alsijil/class_register/lesson.html:248
 #: templates/alsijil/class_register/person.html:110
 #: templates/alsijil/partials/persons_with_stats.html:17
 #: templates/alsijil/partials/persons_with_stats.html:34
@@ -465,10 +535,55 @@ msgstr "Verspätete Personen:"
 msgid "Tardiness"
 msgstr "Verspätung"
 
-#: templates/alsijil/class_register/lesson.html:267
+#: templates/alsijil/class_register/lesson.html:271
 msgid "Tardiness (in m)"
 msgstr "Verspätung (in m)"
 
+#: templates/alsijil/class_register/lesson.html:364
+#, fuzzy, python-format
+#| msgid ""
+#| "\n"
+#| "          Previous %(subject)s lesson\n"
+#| "        "
+msgid ""
+"\n"
+"            Previous %(subject)s lesson\n"
+"          "
+msgstr ""
+"\n"
+"          Vorherige %(subject)s Stunde\n"
+"        "
+
+#: templates/alsijil/class_register/lesson.html:372
+#, fuzzy, python-format
+#| msgid ""
+#| "\n"
+#| "          Next %(subject)s lesson\n"
+#| "        "
+msgid ""
+"\n"
+"            Next %(subject)s lesson\n"
+"          "
+msgstr ""
+"\n"
+"          Nächste %(subject)s Stunde\n"
+"        "
+
+#: templates/alsijil/class_register/lesson.html:387
+#, fuzzy
+#| msgid ""
+#| "\n"
+#| "                  There are no affected lessons. Registering this absence won't have any effect.\n"
+#| "                "
+msgid ""
+"\n"
+"                This lesson overlaps with holidays and can't be edited.\n"
+"              "
+msgstr ""
+"\n"
+"                  Es gibt keine betroffenen Stunden. Das Eintragen dieser Abwesenheit wird keinen Effekt haben.\n"
+"                "
+
 #: templates/alsijil/class_register/person.html:8
 msgid "Class register: person"
 msgstr "Klassenbuch: Person"
@@ -578,44 +693,44 @@ msgstr ""
 "KW %(week)s: \n"
 "%(instance)s"
 
-#: templates/alsijil/class_register/week_view.html:84
+#: templates/alsijil/class_register/week_view.html:100
 msgid "Period"
 msgstr "Stunde"
 
-#: templates/alsijil/class_register/week_view.html:86
+#: templates/alsijil/class_register/week_view.html:102
 msgid "Groups"
 msgstr "Gruppen"
 
-#: templates/alsijil/class_register/week_view.html:88
-#: templates/alsijil/class_register/week_view.html:163
+#: templates/alsijil/class_register/week_view.html:104
+#: templates/alsijil/class_register/week_view.html:186
 #: templates/alsijil/print/full_register.html:169
 #: templates/alsijil/print/full_register.html:200
 msgid "Subject"
 msgstr "Fach"
 
-#: templates/alsijil/class_register/week_view.html:89
-#: templates/alsijil/class_register/week_view.html:173
+#: templates/alsijil/class_register/week_view.html:105
+#: templates/alsijil/class_register/week_view.html:196
 msgid "Teachers"
 msgstr "Lehrkräfte"
 
-#: templates/alsijil/class_register/week_view.html:262
+#: templates/alsijil/class_register/week_view.html:288
 msgid "unexcused"
 msgstr "unentschuldigt"
 
-#: templates/alsijil/class_register/week_view.html:265
+#: templates/alsijil/class_register/week_view.html:291
 msgid "Summed up tardiness"
 msgstr "Summierte Verspätung"
 
-#: templates/alsijil/class_register/week_view.html:268
+#: templates/alsijil/class_register/week_view.html:294
 #: templates/alsijil/partials/persons_with_stats.html:94
 msgid "Count of tardiness"
 msgstr "Anzahl der Verspätungen"
 
-#: templates/alsijil/class_register/week_view.html:297
+#: templates/alsijil/class_register/week_view.html:323
 msgid "No lessons available"
 msgstr "Keine Stunden verfügbar"
 
-#: templates/alsijil/class_register/week_view.html:300
+#: templates/alsijil/class_register/week_view.html:326
 msgid ""
 "\n"
 "            There are no lessons for the selected group or teacher in this week.\n"
@@ -691,7 +806,7 @@ msgid "Data complete"
 msgstr "Daten vollständig"
 
 #: templates/alsijil/partials/lesson_status_icon.html:12
-#: templates/alsijil/print/full_register.html:406
+#: templates/alsijil/print/full_register.html:404
 msgid "Lesson cancelled"
 msgstr "Stunde ist ausgefallen"
 
@@ -708,9 +823,9 @@ msgid "Substitution"
 msgstr "Vertretung"
 
 #: templates/alsijil/partials/mark_as_buttons.html:4
-#: templates/alsijil/print/full_register.html:335
-#: templates/alsijil/print/full_register.html:424
-#: templates/alsijil/print/full_register.html:439
+#: templates/alsijil/print/full_register.html:334
+#: templates/alsijil/print/full_register.html:422
+#: templates/alsijil/print/full_register.html:437
 msgid "e"
 msgstr "e"
 
@@ -880,17 +995,17 @@ msgid "Date"
 msgstr "Datum"
 
 #: templates/alsijil/print/full_register.html:309
-#: templates/alsijil/print/full_register.html:369
+#: templates/alsijil/print/full_register.html:367
 msgid "Pe."
 msgstr "Std."
 
 #: templates/alsijil/print/full_register.html:310
-#: templates/alsijil/print/full_register.html:370
+#: templates/alsijil/print/full_register.html:368
 msgid "Subj."
 msgstr "Fa."
 
 #: templates/alsijil/print/full_register.html:311
-#: templates/alsijil/print/full_register.html:374
+#: templates/alsijil/print/full_register.html:372
 msgid "Te."
 msgstr "Lk."
 
@@ -898,73 +1013,73 @@ msgstr "Lk."
 msgid "Tard."
 msgstr "Verspät."
 
-#: templates/alsijil/print/full_register.html:330
+#: templates/alsijil/print/full_register.html:329
 msgid "Yes"
 msgstr "Ja"
 
-#: templates/alsijil/print/full_register.html:363
+#: templates/alsijil/print/full_register.html:361
 msgid "Lesson documentation for week"
 msgstr "Unterrichtsdokumentation für Woche"
 
-#: templates/alsijil/print/full_register.html:373
+#: templates/alsijil/print/full_register.html:371
 msgid "Notes"
 msgstr "Notizen"
 
-#: views.py:65
+#: views.py:68
 msgid "You either selected an invalid lesson or there is currently no lesson in progress."
 msgstr ""
 "Sie haben eine ungültige Stunde ausgewählt oder es\n"
 "      läuft momentan keine Stunde."
 
-#: views.py:90
+#: views.py:93
 msgid "You are not allowed to create a lesson documentation for a lesson in the future."
 msgstr "Ihnen ist es nicht erlaubt, eine Eintragung für eine Unterrichtsstunde in der Zukunft vorzunehmen."
 
-#: views.py:127
+#: views.py:141
 msgid "The lesson documentation has been saved."
 msgstr "Die Stunden-Dokumentation wurde gespeichert."
 
-#: views.py:151
+#: views.py:165
 msgid "The personal notes have been saved."
 msgstr "Die persönlichen Notizen wurden gespeichert."
 
-#: views.py:570
+#: views.py:591
 msgid "The absences have been marked as excused."
 msgstr "Die Fehlzeiten wurden als entschuldigt markiert."
 
-#: views.py:585
+#: views.py:606
 msgid "The absence has been marked as excused."
 msgstr "Die Fehlzeit wurde als entschuldigt markiert."
 
-#: views.py:721
+#: views.py:749
 msgid "The absence has been saved."
 msgstr "Die Abwesenheit wurde gespeichert."
 
-#: views.py:741
+#: views.py:770
 msgid "The personal note has been deleted."
 msgstr "Die persönliche Notiz wurde gelöscht."
 
-#: views.py:762
+#: views.py:792
 msgid "The extra mark has been created."
 msgstr "Die zusätzliche Markierung wurde erstellt."
 
-#: views.py:773
+#: views.py:804
 msgid "The extra mark has been saved."
 msgstr "Die zusätzliche Markierung wurde gespeichert."
 
-#: views.py:783
+#: views.py:815
 msgid "The extra mark has been deleted."
 msgstr "Die zusätzliche Markierung wurde gelöscht."
 
-#: views.py:803
+#: views.py:836
 msgid "The excuse type has been created."
 msgstr "Die Entschuldigungsart wurde erstellt."
 
-#: views.py:814
+#: views.py:848
 msgid "The excuse type has been saved."
 msgstr "Die Entschuldigunsart wurde gespeichert."
 
-#: views.py:824
+#: views.py:859
 msgid "The excuse type has been deleted."
 msgstr "Die Entschuldigungsart wurde gelöscht."
 
diff --git a/aleksis/apps/alsijil/locale/fr/LC_MESSAGES/django.po b/aleksis/apps/alsijil/locale/fr/LC_MESSAGES/django.po
index 404d2879d67b75879d9fbae9e3f467a4f78e4f96..d848e625848478871d3a2f37c74f913a506feaef 100644
--- a/aleksis/apps/alsijil/locale/fr/LC_MESSAGES/django.po
+++ b/aleksis/apps/alsijil/locale/fr/LC_MESSAGES/django.po
@@ -7,7 +7,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2020-12-05 21:26+0100\n"
+"POT-Creation-Date: 2021-01-22 22:01+0100\n"
 "PO-Revision-Date: 2020-07-26 14:08+0000\n"
 "Last-Translator: Marlene Grundey <grundema@katharineum.de>\n"
 "Language-Team: French <https://translate.edugit.org/projects/aleksis/aleksis-app-alsijil/fr/>\n"
@@ -18,11 +18,73 @@ msgstr ""
 "Plural-Forms: nplurals=2; plural=n > 1;\n"
 "X-Generator: Weblate 4.0.1\n"
 
+#: data_checks.py:15
+msgid "Delete object"
+msgstr ""
+
+#: data_checks.py:25
+msgid "Set current groups"
+msgstr ""
+
+#: data_checks.py:36
+#, fuzzy
+#| msgid "Relevant personal notes"
+msgid "Reset personal note to defaults"
+msgstr "Notes personnelles importantes"
+
+#: data_checks.py:48
+msgid "Ensure that there are no personal notes in cancelled lessons"
+msgstr ""
+
+#: data_checks.py:49
+#, fuzzy
+#| msgid "Lesson documentation for calendar week"
+msgid "The personal note is related to a cancelled lesson."
+msgstr "Documentation de cours pour la semaine calendrier"
+
+#: data_checks.py:72
+msgid "Ensure that 'groups_of_person' is set for every personal note"
+msgstr ""
+
+#: data_checks.py:73
+msgid "The personal note has no group in 'groups_of_person'."
+msgstr ""
+
+#: data_checks.py:107
+msgid "Ensure that there are no filled out lesson documentations on holidays"
+msgstr ""
+
+#: data_checks.py:108
+#, fuzzy
+#| msgid "Lesson documentation for calendar week"
+msgid "The lesson documentation is on holidays."
+msgstr "Documentation de cours pour la semaine calendrier"
+
+#: data_checks.py:143
+msgid "Ensure that there are no filled out personal notes on holidays"
+msgstr ""
+
+#: data_checks.py:144
+#, fuzzy
+#| msgid "Lesson documentation for calendar week"
+msgid "The personal note is on holidays."
+msgstr "Documentation de cours pour la semaine calendrier"
+
+#: data_checks.py:174
+msgid "Ensure that there are no excused personal notes without an absence"
+msgstr ""
+
+#: data_checks.py:175
+#, fuzzy
+#| msgid "Lesson documentation for calendar week"
+msgid "The personal note is marked as excused, but not as absent."
+msgstr "Documentation de cours pour la semaine calendrier"
+
 #: forms.py:29
 msgid "Homework for the next lesson"
 msgstr ""
 
-#: forms.py:54 templates/alsijil/class_register/week_view.html:168
+#: forms.py:54 templates/alsijil/class_register/week_view.html:191
 #: templates/alsijil/print/full_register.html:199
 msgid "Group"
 msgstr "Groupe"
@@ -57,16 +119,16 @@ msgid "End period"
 msgstr "De la période"
 
 #: forms.py:130 templates/alsijil/absences/register_confirm.html:52
-#: templates/alsijil/class_register/lesson.html:243
+#: templates/alsijil/class_register/lesson.html:247
 #: templates/alsijil/class_register/person.html:207
-#: templates/alsijil/class_register/week_view.html:261
+#: templates/alsijil/class_register/week_view.html:287
 #: templates/alsijil/print/full_register.html:75
 #: templates/alsijil/print/full_register.html:312
 msgid "Absent"
 msgstr "Absent(e)"
 
 #: forms.py:131 templates/alsijil/absences/register_confirm.html:56
-#: templates/alsijil/class_register/lesson.html:245
+#: templates/alsijil/class_register/lesson.html:249
 #: templates/alsijil/class_register/person.html:98
 #: templates/alsijil/class_register/person.html:215
 #: templates/alsijil/partials/mark_as_buttons.html:2
@@ -77,16 +139,16 @@ msgstr "Absent(e)"
 msgid "Excused"
 msgstr "Excusé"
 
-#: forms.py:133 models.py:37 models.py:64
-#: templates/alsijil/class_register/lesson.html:246
-#: templates/alsijil/class_register/lesson.html:281
+#: forms.py:133 models.py:45 models.py:79
+#: templates/alsijil/class_register/lesson.html:250
+#: templates/alsijil/class_register/lesson.html:285
 #, fuzzy
 #| msgid "Excused"
 msgid "Excuse type"
 msgstr "Excusé"
 
-#: forms.py:138 templates/alsijil/class_register/lesson.html:248
-#: templates/alsijil/class_register/lesson.html:302
+#: forms.py:138 templates/alsijil/class_register/lesson.html:252
+#: templates/alsijil/class_register/lesson.html:306
 #: templates/alsijil/print/full_register.html:314
 msgid "Remarks"
 msgstr "Remarque"
@@ -121,7 +183,7 @@ msgstr "Vue d'ensemble personnelle"
 msgid "My students"
 msgstr ""
 
-#: menus.py:71 models.py:38 templates/alsijil/excuse_type/list.html:8
+#: menus.py:71 models.py:46 templates/alsijil/excuse_type/list.html:8
 #: templates/alsijil/excuse_type/list.html:9
 #: templates/alsijil/partials/legend.html:26
 #, fuzzy
@@ -129,8 +191,8 @@ msgstr ""
 msgid "Excuse types"
 msgstr "Excusé"
 
-#: menus.py:82 models.py:70 models.py:201
-#: templates/alsijil/class_register/lesson.html:247
+#: menus.py:82 models.py:84 models.py:232
+#: templates/alsijil/class_register/lesson.html:251
 #: templates/alsijil/extra_mark/list.html:8
 #: templates/alsijil/extra_mark/list.html:9
 #: templates/alsijil/partials/legend.html:41
@@ -185,85 +247,85 @@ msgstr ""
 msgid "Can register an absence for a person"
 msgstr "Registre de la classe"
 
-#: models.py:25 models.py:188
+#: models.py:33 models.py:219
 #, fuzzy
 #| msgid "First name"
 msgid "Short name"
 msgstr "Prénom"
 
-#: models.py:26 models.py:189 templates/alsijil/class_register/groups.html:20
+#: models.py:34 models.py:220 templates/alsijil/class_register/groups.html:20
 #: templates/alsijil/partials/persons_with_stats.html:14
 #: templates/alsijil/partials/persons_with_stats.html:24
 msgid "Name"
 msgstr ""
 
-#: models.py:54 models.py:121
+#: models.py:69 models.py:144
 msgid "Year"
 msgstr ""
 
-#: models.py:101
+#: models.py:122
 #, fuzzy
 #| msgid "Personal notes"
 msgid "Personal note"
 msgstr "Notes personnelles"
 
-#: models.py:102 templates/alsijil/class_register/lesson.html:101
-#: templates/alsijil/class_register/lesson.html:233
-#: templates/alsijil/class_register/week_view.html:68
-#: templates/alsijil/class_register/week_view.html:242
+#: models.py:123 templates/alsijil/class_register/lesson.html:105
+#: templates/alsijil/class_register/lesson.html:237
+#: templates/alsijil/class_register/week_view.html:71
+#: templates/alsijil/class_register/week_view.html:267
 msgid "Personal notes"
 msgstr "Notes personnelles"
 
-#: models.py:127 templates/alsijil/class_register/lesson.html:129
-#: templates/alsijil/class_register/week_view.html:90
-#: templates/alsijil/class_register/week_view.html:177
-#: templates/alsijil/print/full_register.html:371
+#: models.py:150 templates/alsijil/class_register/lesson.html:133
+#: templates/alsijil/class_register/week_view.html:106
+#: templates/alsijil/class_register/week_view.html:200
+#: templates/alsijil/print/full_register.html:369
 msgid "Lesson topic"
 msgstr "Sujet de cours"
 
-#: models.py:128 templates/alsijil/class_register/lesson.html:137
-#: templates/alsijil/class_register/week_view.html:91
-#: templates/alsijil/class_register/week_view.html:183
-#: templates/alsijil/class_register/week_view.html:216
-#: templates/alsijil/print/full_register.html:372
+#: models.py:151 templates/alsijil/class_register/lesson.html:141
+#: templates/alsijil/class_register/week_view.html:107
+#: templates/alsijil/class_register/week_view.html:206
+#: templates/alsijil/class_register/week_view.html:239
+#: templates/alsijil/print/full_register.html:370
 msgid "Homework"
 msgstr "Devoirs"
 
-#: models.py:129 templates/alsijil/class_register/lesson.html:145
-#: templates/alsijil/class_register/week_view.html:92
-#: templates/alsijil/class_register/week_view.html:189
-#: templates/alsijil/class_register/week_view.html:222
+#: models.py:152 templates/alsijil/class_register/lesson.html:149
+#: templates/alsijil/class_register/week_view.html:108
+#: templates/alsijil/class_register/week_view.html:212
+#: templates/alsijil/class_register/week_view.html:245
 #, fuzzy
 #| msgid "Group"
 msgid "Group note"
 msgstr "Groupe"
 
-#: models.py:171 templates/alsijil/class_register/lesson.html:97
-#: templates/alsijil/class_register/lesson.html:120
+#: models.py:202 templates/alsijil/class_register/lesson.html:101
+#: templates/alsijil/class_register/lesson.html:124
 msgid "Lesson documentation"
 msgstr "Documentation de cours"
 
-#: models.py:172 templates/alsijil/class_register/week_view.html:67
+#: models.py:203 templates/alsijil/class_register/week_view.html:68
 #, fuzzy
 #| msgid "Lesson documentation"
 msgid "Lesson documentations"
 msgstr "Documentation de cours"
 
-#: models.py:200
+#: models.py:231
 msgid "Extra mark"
 msgstr ""
 
-#: models.py:208
+#: models.py:239
 msgid "Can view week overview"
 msgstr ""
 
-#: models.py:209
+#: models.py:240
 #, fuzzy
 #| msgid "Register absence"
 msgid "Can register absence"
 msgstr "Registre de Absence"
 
-#: models.py:210
+#: models.py:241
 #, fuzzy
 #| msgid "List of all personal note filters"
 msgid "Can list all personal note filters"
@@ -297,6 +359,12 @@ msgstr ""
 msgid "Lessons in the past are not affected by this setting, you can open them whenever you want."
 msgstr ""
 
+#: preferences.py:68
+#, fuzzy
+#| msgid "Teachers and lessons in group"
+msgid "Allow teachers to add data for lessons in holidays"
+msgstr "Profs et cours en groupe"
+
 #: tables.py:16 tables.py:36
 msgid "Edit"
 msgstr ""
@@ -308,13 +376,13 @@ msgstr ""
 #: templates/alsijil/absences/register.html:5
 #: templates/alsijil/absences/register.html:6
 #: templates/alsijil/class_register/person.html:30
-#: templates/alsijil/class_register/week_view.html:256
+#: templates/alsijil/class_register/week_view.html:282
 #: templates/alsijil/partials/persons_with_stats.html:115
 msgid "Register absence"
 msgstr "Registre de Absence"
 
 #: templates/alsijil/absences/register.html:9
-#: templates/alsijil/class_register/lesson.html:242
+#: templates/alsijil/class_register/lesson.html:246
 msgid "Person"
 msgstr "Personne"
 
@@ -432,14 +500,13 @@ msgid "My next lesson"
 msgstr "Lecon actuelle"
 
 #: templates/alsijil/class_register/lesson.html:46
-#: templates/alsijil/class_register/lesson.html:167
+#: templates/alsijil/class_register/lesson.html:171
 #, fuzzy, python-format
 #| msgid "From period"
 msgid "%(period)s. period"
 msgstr "De la période"
 
-#: templates/alsijil/class_register/lesson.html:77
-#: templates/alsijil/class_register/lesson.html:359
+#: templates/alsijil/class_register/lesson.html:79
 #, python-format
 msgid ""
 "\n"
@@ -447,8 +514,7 @@ msgid ""
 "        "
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:85
-#: templates/alsijil/class_register/lesson.html:367
+#: templates/alsijil/class_register/lesson.html:87
 #, python-format
 msgid ""
 "\n"
@@ -456,44 +522,44 @@ msgid ""
 "        "
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:107
+#: templates/alsijil/class_register/lesson.html:111
 #, fuzzy
 #| msgid "Current lesson"
 msgid "Previous lesson"
 msgstr "Lecon actuelle"
 
-#: templates/alsijil/class_register/lesson.html:111
-#: templates/alsijil/class_register/lesson.html:342
+#: templates/alsijil/class_register/lesson.html:115
+#: templates/alsijil/class_register/lesson.html:346
 msgid "Change history"
 msgstr "Changement d' histoire"
 
-#: templates/alsijil/class_register/lesson.html:166
+#: templates/alsijil/class_register/lesson.html:170
 msgid "Overview: Previous lesson"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:173
+#: templates/alsijil/class_register/lesson.html:177
 msgid "Lesson topic of previous lesson:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:180
+#: templates/alsijil/class_register/lesson.html:184
 msgid "Homework for this lesson:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:187
+#: templates/alsijil/class_register/lesson.html:191
 msgid "Group notes for previous lesson:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:194
+#: templates/alsijil/class_register/lesson.html:198
 #, fuzzy
 #| msgid "Absences"
 msgid "Absent persons:"
 msgstr "Absences"
 
-#: templates/alsijil/class_register/lesson.html:201
+#: templates/alsijil/class_register/lesson.html:205
 msgid "Late persons:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:244
+#: templates/alsijil/class_register/lesson.html:248
 #: templates/alsijil/class_register/person.html:110
 #: templates/alsijil/partials/persons_with_stats.html:17
 #: templates/alsijil/partials/persons_with_stats.html:34
@@ -502,12 +568,43 @@ msgstr ""
 msgid "Tardiness"
 msgstr "Retard"
 
-#: templates/alsijil/class_register/lesson.html:267
+#: templates/alsijil/class_register/lesson.html:271
 #, fuzzy
 #| msgid "Tardiness"
 msgid "Tardiness (in m)"
 msgstr "Retard"
 
+#: templates/alsijil/class_register/lesson.html:364
+#, python-format
+msgid ""
+"\n"
+"            Previous %(subject)s lesson\n"
+"          "
+msgstr ""
+
+#: templates/alsijil/class_register/lesson.html:372
+#, python-format
+msgid ""
+"\n"
+"            Next %(subject)s lesson\n"
+"          "
+msgstr ""
+
+#: templates/alsijil/class_register/lesson.html:387
+#, fuzzy
+#| msgid ""
+#| "\n"
+#| "            There are no lessons for the selected group, teacher, room or time.\n"
+#| "          "
+msgid ""
+"\n"
+"                This lesson overlaps with holidays and can't be edited.\n"
+"              "
+msgstr ""
+"\n"
+"            Il n' y a pas des cours pour le groupe sélectionné, les profs, le salle ou le temps.\n"
+"          "
+
 #: templates/alsijil/class_register/person.html:8
 #, fuzzy
 #| msgid "Class register"
@@ -616,48 +713,48 @@ msgid ""
 "      %(instance)s"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:84
+#: templates/alsijil/class_register/week_view.html:100
 msgid "Period"
 msgstr "Période"
 
-#: templates/alsijil/class_register/week_view.html:86
+#: templates/alsijil/class_register/week_view.html:102
 #, fuzzy
 #| msgid "Group"
 msgid "Groups"
 msgstr "Groupe"
 
-#: templates/alsijil/class_register/week_view.html:88
-#: templates/alsijil/class_register/week_view.html:163
+#: templates/alsijil/class_register/week_view.html:104
+#: templates/alsijil/class_register/week_view.html:186
 #: templates/alsijil/print/full_register.html:169
 #: templates/alsijil/print/full_register.html:200
 msgid "Subject"
 msgstr "Sujet"
 
-#: templates/alsijil/class_register/week_view.html:89
-#: templates/alsijil/class_register/week_view.html:173
+#: templates/alsijil/class_register/week_view.html:105
+#: templates/alsijil/class_register/week_view.html:196
 msgid "Teachers"
 msgstr "Profs"
 
-#: templates/alsijil/class_register/week_view.html:262
+#: templates/alsijil/class_register/week_view.html:288
 msgid "unexcused"
 msgstr "Injustifié(e)"
 
-#: templates/alsijil/class_register/week_view.html:265
+#: templates/alsijil/class_register/week_view.html:291
 msgid "Summed up tardiness"
 msgstr "Résumé des retards"
 
-#: templates/alsijil/class_register/week_view.html:268
+#: templates/alsijil/class_register/week_view.html:294
 #: templates/alsijil/partials/persons_with_stats.html:94
 #, fuzzy
 #| msgid "Summed up tardiness"
 msgid "Count of tardiness"
 msgstr "Résumé des retards"
 
-#: templates/alsijil/class_register/week_view.html:297
+#: templates/alsijil/class_register/week_view.html:323
 msgid "No lessons available"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:300
+#: templates/alsijil/class_register/week_view.html:326
 #, fuzzy
 #| msgid ""
 #| "\n"
@@ -736,7 +833,7 @@ msgid "Data complete"
 msgstr ""
 
 #: templates/alsijil/partials/lesson_status_icon.html:12
-#: templates/alsijil/print/full_register.html:406
+#: templates/alsijil/print/full_register.html:404
 msgid "Lesson cancelled"
 msgstr "Cours annulés"
 
@@ -753,9 +850,9 @@ msgid "Substitution"
 msgstr ""
 
 #: templates/alsijil/partials/mark_as_buttons.html:4
-#: templates/alsijil/print/full_register.html:335
-#: templates/alsijil/print/full_register.html:424
-#: templates/alsijil/print/full_register.html:439
+#: templates/alsijil/print/full_register.html:334
+#: templates/alsijil/print/full_register.html:422
+#: templates/alsijil/print/full_register.html:437
 msgid "e"
 msgstr "e"
 
@@ -917,17 +1014,17 @@ msgid "Date"
 msgstr "Date"
 
 #: templates/alsijil/print/full_register.html:309
-#: templates/alsijil/print/full_register.html:369
+#: templates/alsijil/print/full_register.html:367
 msgid "Pe."
 msgstr ""
 
 #: templates/alsijil/print/full_register.html:310
-#: templates/alsijil/print/full_register.html:370
+#: templates/alsijil/print/full_register.html:368
 msgid "Subj."
 msgstr ""
 
 #: templates/alsijil/print/full_register.html:311
-#: templates/alsijil/print/full_register.html:374
+#: templates/alsijil/print/full_register.html:372
 msgid "Te."
 msgstr ""
 
@@ -935,81 +1032,81 @@ msgstr ""
 msgid "Tard."
 msgstr ""
 
-#: templates/alsijil/print/full_register.html:330
+#: templates/alsijil/print/full_register.html:329
 msgid "Yes"
 msgstr "Oui"
 
-#: templates/alsijil/print/full_register.html:363
+#: templates/alsijil/print/full_register.html:361
 #, fuzzy
 #| msgid "Lesson documentation for calendar week"
 msgid "Lesson documentation for week"
 msgstr "Documentation de cours pour la semaine calendrier"
 
-#: templates/alsijil/print/full_register.html:373
+#: templates/alsijil/print/full_register.html:371
 msgid "Notes"
 msgstr "Notes"
 
-#: views.py:65
+#: views.py:68
 msgid "You either selected an invalid lesson or there is currently no lesson in progress."
 msgstr ""
 
-#: views.py:90
+#: views.py:93
 msgid "You are not allowed to create a lesson documentation for a lesson in the future."
 msgstr ""
 
-#: views.py:127
+#: views.py:141
 #, fuzzy
 #| msgid "Lesson documentation for calendar week"
 msgid "The lesson documentation has been saved."
 msgstr "Documentation de cours pour la semaine calendrier"
 
-#: views.py:151
+#: views.py:165
 msgid "The personal notes have been saved."
 msgstr ""
 
-#: views.py:570
+#: views.py:591
 msgid "The absences have been marked as excused."
 msgstr ""
 
-#: views.py:585
+#: views.py:606
 msgid "The absence has been marked as excused."
 msgstr ""
 
-#: views.py:721
+#: views.py:749
 msgid "The absence has been saved."
 msgstr ""
 
-#: views.py:741
+#: views.py:770
 #, fuzzy
 #| msgid "Lesson documentation for calendar week"
 msgid "The personal note has been deleted."
 msgstr "Documentation de cours pour la semaine calendrier"
 
-#: views.py:762
+#: views.py:792
 #, fuzzy
 #| msgid "Lesson documentation for calendar week"
 msgid "The extra mark has been created."
 msgstr "Documentation de cours pour la semaine calendrier"
 
-#: views.py:773
+#: views.py:804
 #, fuzzy
 #| msgid "Lesson documentation for calendar week"
 msgid "The extra mark has been saved."
 msgstr "Documentation de cours pour la semaine calendrier"
 
-#: views.py:783
+#: views.py:815
 msgid "The extra mark has been deleted."
 msgstr ""
 
-#: views.py:803
+#: views.py:836
 msgid "The excuse type has been created."
 msgstr ""
 
-#: views.py:814
+#: views.py:848
 msgid "The excuse type has been saved."
 msgstr ""
 
-#: views.py:824
+#: views.py:859
 msgid "The excuse type has been deleted."
 msgstr ""
 
diff --git a/aleksis/apps/alsijil/locale/la/LC_MESSAGES/django.po b/aleksis/apps/alsijil/locale/la/LC_MESSAGES/django.po
index 053c32a5484cf531503f41a76d6e56ff51bcd59c..f084ed1f6bee2fb6607fb04229f5c1e492a7fd7d 100644
--- a/aleksis/apps/alsijil/locale/la/LC_MESSAGES/django.po
+++ b/aleksis/apps/alsijil/locale/la/LC_MESSAGES/django.po
@@ -7,7 +7,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2020-12-05 21:26+0100\n"
+"POT-Creation-Date: 2021-01-22 22:01+0100\n"
 "PO-Revision-Date: 2020-07-26 14:08+0000\n"
 "Last-Translator: Julian <leuckerj@gmail.com>\n"
 "Language-Team: Latin <https://translate.edugit.org/projects/aleksis/aleksis-app-alsijil/la/>\n"
@@ -18,11 +18,63 @@ msgstr ""
 "Plural-Forms: nplurals=2; plural=n != 1;\n"
 "X-Generator: Weblate 4.0.1\n"
 
+#: data_checks.py:15
+msgid "Delete object"
+msgstr ""
+
+#: data_checks.py:25
+msgid "Set current groups"
+msgstr ""
+
+#: data_checks.py:36
+msgid "Reset personal note to defaults"
+msgstr ""
+
+#: data_checks.py:48
+msgid "Ensure that there are no personal notes in cancelled lessons"
+msgstr ""
+
+#: data_checks.py:49
+msgid "The personal note is related to a cancelled lesson."
+msgstr ""
+
+#: data_checks.py:72
+msgid "Ensure that 'groups_of_person' is set for every personal note"
+msgstr ""
+
+#: data_checks.py:73
+msgid "The personal note has no group in 'groups_of_person'."
+msgstr ""
+
+#: data_checks.py:107
+msgid "Ensure that there are no filled out lesson documentations on holidays"
+msgstr ""
+
+#: data_checks.py:108
+msgid "The lesson documentation is on holidays."
+msgstr ""
+
+#: data_checks.py:143
+msgid "Ensure that there are no filled out personal notes on holidays"
+msgstr ""
+
+#: data_checks.py:144
+msgid "The personal note is on holidays."
+msgstr ""
+
+#: data_checks.py:174
+msgid "Ensure that there are no excused personal notes without an absence"
+msgstr ""
+
+#: data_checks.py:175
+msgid "The personal note is marked as excused, but not as absent."
+msgstr ""
+
 #: forms.py:29
 msgid "Homework for the next lesson"
 msgstr ""
 
-#: forms.py:54 templates/alsijil/class_register/week_view.html:168
+#: forms.py:54 templates/alsijil/class_register/week_view.html:191
 #: templates/alsijil/print/full_register.html:199
 msgid "Group"
 msgstr "Grex"
@@ -53,16 +105,16 @@ msgid "End period"
 msgstr ""
 
 #: forms.py:130 templates/alsijil/absences/register_confirm.html:52
-#: templates/alsijil/class_register/lesson.html:243
+#: templates/alsijil/class_register/lesson.html:247
 #: templates/alsijil/class_register/person.html:207
-#: templates/alsijil/class_register/week_view.html:261
+#: templates/alsijil/class_register/week_view.html:287
 #: templates/alsijil/print/full_register.html:75
 #: templates/alsijil/print/full_register.html:312
 msgid "Absent"
 msgstr ""
 
 #: forms.py:131 templates/alsijil/absences/register_confirm.html:56
-#: templates/alsijil/class_register/lesson.html:245
+#: templates/alsijil/class_register/lesson.html:249
 #: templates/alsijil/class_register/person.html:98
 #: templates/alsijil/class_register/person.html:215
 #: templates/alsijil/partials/mark_as_buttons.html:2
@@ -73,14 +125,14 @@ msgstr ""
 msgid "Excused"
 msgstr ""
 
-#: forms.py:133 models.py:37 models.py:64
-#: templates/alsijil/class_register/lesson.html:246
-#: templates/alsijil/class_register/lesson.html:281
+#: forms.py:133 models.py:45 models.py:79
+#: templates/alsijil/class_register/lesson.html:250
+#: templates/alsijil/class_register/lesson.html:285
 msgid "Excuse type"
 msgstr ""
 
-#: forms.py:138 templates/alsijil/class_register/lesson.html:248
-#: templates/alsijil/class_register/lesson.html:302
+#: forms.py:138 templates/alsijil/class_register/lesson.html:252
+#: templates/alsijil/class_register/lesson.html:306
 #: templates/alsijil/print/full_register.html:314
 msgid "Remarks"
 msgstr ""
@@ -113,14 +165,14 @@ msgstr ""
 msgid "My students"
 msgstr ""
 
-#: menus.py:71 models.py:38 templates/alsijil/excuse_type/list.html:8
+#: menus.py:71 models.py:46 templates/alsijil/excuse_type/list.html:8
 #: templates/alsijil/excuse_type/list.html:9
 #: templates/alsijil/partials/legend.html:26
 msgid "Excuse types"
 msgstr ""
 
-#: menus.py:82 models.py:70 models.py:201
-#: templates/alsijil/class_register/lesson.html:247
+#: menus.py:82 models.py:84 models.py:232
+#: templates/alsijil/class_register/lesson.html:251
 #: templates/alsijil/extra_mark/list.html:8
 #: templates/alsijil/extra_mark/list.html:9
 #: templates/alsijil/partials/legend.html:41
@@ -165,81 +217,81 @@ msgstr ""
 msgid "Can register an absence for a person"
 msgstr ""
 
-#: models.py:25 models.py:188
+#: models.py:33 models.py:219
 #, fuzzy
 #| msgid "First name"
 msgid "Short name"
 msgstr "Primus nomen"
 
-#: models.py:26 models.py:189 templates/alsijil/class_register/groups.html:20
+#: models.py:34 models.py:220 templates/alsijil/class_register/groups.html:20
 #: templates/alsijil/partials/persons_with_stats.html:14
 #: templates/alsijil/partials/persons_with_stats.html:24
 msgid "Name"
 msgstr ""
 
-#: models.py:54 models.py:121
+#: models.py:69 models.py:144
 msgid "Year"
 msgstr ""
 
-#: models.py:101
+#: models.py:122
 #, fuzzy
 #| msgid "Person"
 msgid "Personal note"
 msgstr "Persona"
 
-#: models.py:102 templates/alsijil/class_register/lesson.html:101
-#: templates/alsijil/class_register/lesson.html:233
-#: templates/alsijil/class_register/week_view.html:68
-#: templates/alsijil/class_register/week_view.html:242
+#: models.py:123 templates/alsijil/class_register/lesson.html:105
+#: templates/alsijil/class_register/lesson.html:237
+#: templates/alsijil/class_register/week_view.html:71
+#: templates/alsijil/class_register/week_view.html:267
 msgid "Personal notes"
 msgstr ""
 
-#: models.py:127 templates/alsijil/class_register/lesson.html:129
-#: templates/alsijil/class_register/week_view.html:90
-#: templates/alsijil/class_register/week_view.html:177
-#: templates/alsijil/print/full_register.html:371
+#: models.py:150 templates/alsijil/class_register/lesson.html:133
+#: templates/alsijil/class_register/week_view.html:106
+#: templates/alsijil/class_register/week_view.html:200
+#: templates/alsijil/print/full_register.html:369
 msgid "Lesson topic"
 msgstr ""
 
-#: models.py:128 templates/alsijil/class_register/lesson.html:137
-#: templates/alsijil/class_register/week_view.html:91
-#: templates/alsijil/class_register/week_view.html:183
-#: templates/alsijil/class_register/week_view.html:216
-#: templates/alsijil/print/full_register.html:372
+#: models.py:151 templates/alsijil/class_register/lesson.html:141
+#: templates/alsijil/class_register/week_view.html:107
+#: templates/alsijil/class_register/week_view.html:206
+#: templates/alsijil/class_register/week_view.html:239
+#: templates/alsijil/print/full_register.html:370
 msgid "Homework"
 msgstr ""
 
-#: models.py:129 templates/alsijil/class_register/lesson.html:145
-#: templates/alsijil/class_register/week_view.html:92
-#: templates/alsijil/class_register/week_view.html:189
-#: templates/alsijil/class_register/week_view.html:222
+#: models.py:152 templates/alsijil/class_register/lesson.html:149
+#: templates/alsijil/class_register/week_view.html:108
+#: templates/alsijil/class_register/week_view.html:212
+#: templates/alsijil/class_register/week_view.html:245
 #, fuzzy
 #| msgid "Group"
 msgid "Group note"
 msgstr "Grex"
 
-#: models.py:171 templates/alsijil/class_register/lesson.html:97
-#: templates/alsijil/class_register/lesson.html:120
+#: models.py:202 templates/alsijil/class_register/lesson.html:101
+#: templates/alsijil/class_register/lesson.html:124
 msgid "Lesson documentation"
 msgstr ""
 
-#: models.py:172 templates/alsijil/class_register/week_view.html:67
+#: models.py:203 templates/alsijil/class_register/week_view.html:68
 msgid "Lesson documentations"
 msgstr ""
 
-#: models.py:200
+#: models.py:231
 msgid "Extra mark"
 msgstr ""
 
-#: models.py:208
+#: models.py:239
 msgid "Can view week overview"
 msgstr ""
 
-#: models.py:209
+#: models.py:240
 msgid "Can register absence"
 msgstr ""
 
-#: models.py:210
+#: models.py:241
 msgid "Can list all personal note filters"
 msgstr ""
 
@@ -271,6 +323,10 @@ msgstr ""
 msgid "Lessons in the past are not affected by this setting, you can open them whenever you want."
 msgstr ""
 
+#: preferences.py:68
+msgid "Allow teachers to add data for lessons in holidays"
+msgstr ""
+
 #: tables.py:16 tables.py:36
 msgid "Edit"
 msgstr ""
@@ -282,13 +338,13 @@ msgstr ""
 #: templates/alsijil/absences/register.html:5
 #: templates/alsijil/absences/register.html:6
 #: templates/alsijil/class_register/person.html:30
-#: templates/alsijil/class_register/week_view.html:256
+#: templates/alsijil/class_register/week_view.html:282
 #: templates/alsijil/partials/persons_with_stats.html:115
 msgid "Register absence"
 msgstr ""
 
 #: templates/alsijil/absences/register.html:9
-#: templates/alsijil/class_register/lesson.html:242
+#: templates/alsijil/class_register/lesson.html:246
 msgid "Person"
 msgstr "Persona"
 
@@ -390,13 +446,12 @@ msgid "My next lesson"
 msgstr ""
 
 #: templates/alsijil/class_register/lesson.html:46
-#: templates/alsijil/class_register/lesson.html:167
+#: templates/alsijil/class_register/lesson.html:171
 #, python-format
 msgid "%(period)s. period"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:77
-#: templates/alsijil/class_register/lesson.html:359
+#: templates/alsijil/class_register/lesson.html:79
 #, python-format
 msgid ""
 "\n"
@@ -404,8 +459,7 @@ msgid ""
 "        "
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:85
-#: templates/alsijil/class_register/lesson.html:367
+#: templates/alsijil/class_register/lesson.html:87
 #, python-format
 msgid ""
 "\n"
@@ -413,40 +467,40 @@ msgid ""
 "        "
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:107
+#: templates/alsijil/class_register/lesson.html:111
 msgid "Previous lesson"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:111
-#: templates/alsijil/class_register/lesson.html:342
+#: templates/alsijil/class_register/lesson.html:115
+#: templates/alsijil/class_register/lesson.html:346
 msgid "Change history"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:166
+#: templates/alsijil/class_register/lesson.html:170
 msgid "Overview: Previous lesson"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:173
+#: templates/alsijil/class_register/lesson.html:177
 msgid "Lesson topic of previous lesson:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:180
+#: templates/alsijil/class_register/lesson.html:184
 msgid "Homework for this lesson:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:187
+#: templates/alsijil/class_register/lesson.html:191
 msgid "Group notes for previous lesson:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:194
+#: templates/alsijil/class_register/lesson.html:198
 msgid "Absent persons:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:201
+#: templates/alsijil/class_register/lesson.html:205
 msgid "Late persons:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:244
+#: templates/alsijil/class_register/lesson.html:248
 #: templates/alsijil/class_register/person.html:110
 #: templates/alsijil/partials/persons_with_stats.html:17
 #: templates/alsijil/partials/persons_with_stats.html:34
@@ -455,10 +509,33 @@ msgstr ""
 msgid "Tardiness"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:267
+#: templates/alsijil/class_register/lesson.html:271
 msgid "Tardiness (in m)"
 msgstr ""
 
+#: templates/alsijil/class_register/lesson.html:364
+#, python-format
+msgid ""
+"\n"
+"            Previous %(subject)s lesson\n"
+"          "
+msgstr ""
+
+#: templates/alsijil/class_register/lesson.html:372
+#, python-format
+msgid ""
+"\n"
+"            Next %(subject)s lesson\n"
+"          "
+msgstr ""
+
+#: templates/alsijil/class_register/lesson.html:387
+msgid ""
+"\n"
+"                This lesson overlaps with holidays and can't be edited.\n"
+"              "
+msgstr ""
+
 #: templates/alsijil/class_register/person.html:8
 msgid "Class register: person"
 msgstr ""
@@ -563,46 +640,46 @@ msgid ""
 "      %(instance)s"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:84
+#: templates/alsijil/class_register/week_view.html:100
 msgid "Period"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:86
+#: templates/alsijil/class_register/week_view.html:102
 #, fuzzy
 #| msgid "Group"
 msgid "Groups"
 msgstr "Grex"
 
-#: templates/alsijil/class_register/week_view.html:88
-#: templates/alsijil/class_register/week_view.html:163
+#: templates/alsijil/class_register/week_view.html:104
+#: templates/alsijil/class_register/week_view.html:186
 #: templates/alsijil/print/full_register.html:169
 #: templates/alsijil/print/full_register.html:200
 msgid "Subject"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:89
-#: templates/alsijil/class_register/week_view.html:173
+#: templates/alsijil/class_register/week_view.html:105
+#: templates/alsijil/class_register/week_view.html:196
 msgid "Teachers"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:262
+#: templates/alsijil/class_register/week_view.html:288
 msgid "unexcused"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:265
+#: templates/alsijil/class_register/week_view.html:291
 msgid "Summed up tardiness"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:268
+#: templates/alsijil/class_register/week_view.html:294
 #: templates/alsijil/partials/persons_with_stats.html:94
 msgid "Count of tardiness"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:297
+#: templates/alsijil/class_register/week_view.html:323
 msgid "No lessons available"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:300
+#: templates/alsijil/class_register/week_view.html:326
 msgid ""
 "\n"
 "            There are no lessons for the selected group or teacher in this week.\n"
@@ -671,7 +748,7 @@ msgid "Data complete"
 msgstr ""
 
 #: templates/alsijil/partials/lesson_status_icon.html:12
-#: templates/alsijil/print/full_register.html:406
+#: templates/alsijil/print/full_register.html:404
 msgid "Lesson cancelled"
 msgstr ""
 
@@ -688,9 +765,9 @@ msgid "Substitution"
 msgstr ""
 
 #: templates/alsijil/partials/mark_as_buttons.html:4
-#: templates/alsijil/print/full_register.html:335
-#: templates/alsijil/print/full_register.html:424
-#: templates/alsijil/print/full_register.html:439
+#: templates/alsijil/print/full_register.html:334
+#: templates/alsijil/print/full_register.html:422
+#: templates/alsijil/print/full_register.html:437
 msgid "e"
 msgstr ""
 
@@ -848,17 +925,17 @@ msgid "Date"
 msgstr "dies"
 
 #: templates/alsijil/print/full_register.html:309
-#: templates/alsijil/print/full_register.html:369
+#: templates/alsijil/print/full_register.html:367
 msgid "Pe."
 msgstr ""
 
 #: templates/alsijil/print/full_register.html:310
-#: templates/alsijil/print/full_register.html:370
+#: templates/alsijil/print/full_register.html:368
 msgid "Subj."
 msgstr ""
 
 #: templates/alsijil/print/full_register.html:311
-#: templates/alsijil/print/full_register.html:374
+#: templates/alsijil/print/full_register.html:372
 msgid "Te."
 msgstr ""
 
@@ -866,71 +943,71 @@ msgstr ""
 msgid "Tard."
 msgstr ""
 
-#: templates/alsijil/print/full_register.html:330
+#: templates/alsijil/print/full_register.html:329
 msgid "Yes"
 msgstr ""
 
-#: templates/alsijil/print/full_register.html:363
+#: templates/alsijil/print/full_register.html:361
 msgid "Lesson documentation for week"
 msgstr ""
 
-#: templates/alsijil/print/full_register.html:373
+#: templates/alsijil/print/full_register.html:371
 msgid "Notes"
 msgstr ""
 
-#: views.py:65
+#: views.py:68
 msgid "You either selected an invalid lesson or there is currently no lesson in progress."
 msgstr ""
 
-#: views.py:90
+#: views.py:93
 msgid "You are not allowed to create a lesson documentation for a lesson in the future."
 msgstr ""
 
-#: views.py:127
+#: views.py:141
 msgid "The lesson documentation has been saved."
 msgstr ""
 
-#: views.py:151
+#: views.py:165
 msgid "The personal notes have been saved."
 msgstr ""
 
-#: views.py:570
+#: views.py:591
 msgid "The absences have been marked as excused."
 msgstr ""
 
-#: views.py:585
+#: views.py:606
 msgid "The absence has been marked as excused."
 msgstr ""
 
-#: views.py:721
+#: views.py:749
 msgid "The absence has been saved."
 msgstr ""
 
-#: views.py:741
+#: views.py:770
 msgid "The personal note has been deleted."
 msgstr ""
 
-#: views.py:762
+#: views.py:792
 msgid "The extra mark has been created."
 msgstr ""
 
-#: views.py:773
+#: views.py:804
 msgid "The extra mark has been saved."
 msgstr ""
 
-#: views.py:783
+#: views.py:815
 msgid "The extra mark has been deleted."
 msgstr ""
 
-#: views.py:803
+#: views.py:836
 msgid "The excuse type has been created."
 msgstr ""
 
-#: views.py:814
+#: views.py:848
 msgid "The excuse type has been saved."
 msgstr ""
 
-#: views.py:824
+#: views.py:859
 msgid "The excuse type has been deleted."
 msgstr ""
 
diff --git a/aleksis/apps/alsijil/locale/nb_NO/LC_MESSAGES/django.po b/aleksis/apps/alsijil/locale/nb_NO/LC_MESSAGES/django.po
index 219d7af7ff7ca661ccb440d5fab0002ecb546788..4704f58a5eb1586fdaf87d76c815c27f80e81c30 100644
--- a/aleksis/apps/alsijil/locale/nb_NO/LC_MESSAGES/django.po
+++ b/aleksis/apps/alsijil/locale/nb_NO/LC_MESSAGES/django.po
@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2020-12-05 21:26+0100\n"
+"POT-Creation-Date: 2021-01-22 22:01+0100\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -17,11 +17,63 @@ msgstr ""
 "Content-Type: text/plain; charset=UTF-8\n"
 "Content-Transfer-Encoding: 8bit\n"
 
+#: data_checks.py:15
+msgid "Delete object"
+msgstr ""
+
+#: data_checks.py:25
+msgid "Set current groups"
+msgstr ""
+
+#: data_checks.py:36
+msgid "Reset personal note to defaults"
+msgstr ""
+
+#: data_checks.py:48
+msgid "Ensure that there are no personal notes in cancelled lessons"
+msgstr ""
+
+#: data_checks.py:49
+msgid "The personal note is related to a cancelled lesson."
+msgstr ""
+
+#: data_checks.py:72
+msgid "Ensure that 'groups_of_person' is set for every personal note"
+msgstr ""
+
+#: data_checks.py:73
+msgid "The personal note has no group in 'groups_of_person'."
+msgstr ""
+
+#: data_checks.py:107
+msgid "Ensure that there are no filled out lesson documentations on holidays"
+msgstr ""
+
+#: data_checks.py:108
+msgid "The lesson documentation is on holidays."
+msgstr ""
+
+#: data_checks.py:143
+msgid "Ensure that there are no filled out personal notes on holidays"
+msgstr ""
+
+#: data_checks.py:144
+msgid "The personal note is on holidays."
+msgstr ""
+
+#: data_checks.py:174
+msgid "Ensure that there are no excused personal notes without an absence"
+msgstr ""
+
+#: data_checks.py:175
+msgid "The personal note is marked as excused, but not as absent."
+msgstr ""
+
 #: forms.py:29
 msgid "Homework for the next lesson"
 msgstr ""
 
-#: forms.py:54 templates/alsijil/class_register/week_view.html:168
+#: forms.py:54 templates/alsijil/class_register/week_view.html:191
 #: templates/alsijil/print/full_register.html:199
 msgid "Group"
 msgstr ""
@@ -52,16 +104,16 @@ msgid "End period"
 msgstr ""
 
 #: forms.py:130 templates/alsijil/absences/register_confirm.html:52
-#: templates/alsijil/class_register/lesson.html:243
+#: templates/alsijil/class_register/lesson.html:247
 #: templates/alsijil/class_register/person.html:207
-#: templates/alsijil/class_register/week_view.html:261
+#: templates/alsijil/class_register/week_view.html:287
 #: templates/alsijil/print/full_register.html:75
 #: templates/alsijil/print/full_register.html:312
 msgid "Absent"
 msgstr ""
 
 #: forms.py:131 templates/alsijil/absences/register_confirm.html:56
-#: templates/alsijil/class_register/lesson.html:245
+#: templates/alsijil/class_register/lesson.html:249
 #: templates/alsijil/class_register/person.html:98
 #: templates/alsijil/class_register/person.html:215
 #: templates/alsijil/partials/mark_as_buttons.html:2
@@ -72,14 +124,14 @@ msgstr ""
 msgid "Excused"
 msgstr ""
 
-#: forms.py:133 models.py:37 models.py:64
-#: templates/alsijil/class_register/lesson.html:246
-#: templates/alsijil/class_register/lesson.html:281
+#: forms.py:133 models.py:45 models.py:79
+#: templates/alsijil/class_register/lesson.html:250
+#: templates/alsijil/class_register/lesson.html:285
 msgid "Excuse type"
 msgstr ""
 
-#: forms.py:138 templates/alsijil/class_register/lesson.html:248
-#: templates/alsijil/class_register/lesson.html:302
+#: forms.py:138 templates/alsijil/class_register/lesson.html:252
+#: templates/alsijil/class_register/lesson.html:306
 #: templates/alsijil/print/full_register.html:314
 msgid "Remarks"
 msgstr ""
@@ -110,14 +162,14 @@ msgstr ""
 msgid "My students"
 msgstr ""
 
-#: menus.py:71 models.py:38 templates/alsijil/excuse_type/list.html:8
+#: menus.py:71 models.py:46 templates/alsijil/excuse_type/list.html:8
 #: templates/alsijil/excuse_type/list.html:9
 #: templates/alsijil/partials/legend.html:26
 msgid "Excuse types"
 msgstr ""
 
-#: menus.py:82 models.py:70 models.py:201
-#: templates/alsijil/class_register/lesson.html:247
+#: menus.py:82 models.py:84 models.py:232
+#: templates/alsijil/class_register/lesson.html:251
 #: templates/alsijil/extra_mark/list.html:8
 #: templates/alsijil/extra_mark/list.html:9
 #: templates/alsijil/partials/legend.html:41
@@ -162,75 +214,75 @@ msgstr ""
 msgid "Can register an absence for a person"
 msgstr ""
 
-#: models.py:25 models.py:188
+#: models.py:33 models.py:219
 msgid "Short name"
 msgstr ""
 
-#: models.py:26 models.py:189 templates/alsijil/class_register/groups.html:20
+#: models.py:34 models.py:220 templates/alsijil/class_register/groups.html:20
 #: templates/alsijil/partials/persons_with_stats.html:14
 #: templates/alsijil/partials/persons_with_stats.html:24
 msgid "Name"
 msgstr ""
 
-#: models.py:54 models.py:121
+#: models.py:69 models.py:144
 msgid "Year"
 msgstr ""
 
-#: models.py:101
+#: models.py:122
 msgid "Personal note"
 msgstr ""
 
-#: models.py:102 templates/alsijil/class_register/lesson.html:101
-#: templates/alsijil/class_register/lesson.html:233
-#: templates/alsijil/class_register/week_view.html:68
-#: templates/alsijil/class_register/week_view.html:242
+#: models.py:123 templates/alsijil/class_register/lesson.html:105
+#: templates/alsijil/class_register/lesson.html:237
+#: templates/alsijil/class_register/week_view.html:71
+#: templates/alsijil/class_register/week_view.html:267
 msgid "Personal notes"
 msgstr ""
 
-#: models.py:127 templates/alsijil/class_register/lesson.html:129
-#: templates/alsijil/class_register/week_view.html:90
-#: templates/alsijil/class_register/week_view.html:177
-#: templates/alsijil/print/full_register.html:371
+#: models.py:150 templates/alsijil/class_register/lesson.html:133
+#: templates/alsijil/class_register/week_view.html:106
+#: templates/alsijil/class_register/week_view.html:200
+#: templates/alsijil/print/full_register.html:369
 msgid "Lesson topic"
 msgstr ""
 
-#: models.py:128 templates/alsijil/class_register/lesson.html:137
-#: templates/alsijil/class_register/week_view.html:91
-#: templates/alsijil/class_register/week_view.html:183
-#: templates/alsijil/class_register/week_view.html:216
-#: templates/alsijil/print/full_register.html:372
+#: models.py:151 templates/alsijil/class_register/lesson.html:141
+#: templates/alsijil/class_register/week_view.html:107
+#: templates/alsijil/class_register/week_view.html:206
+#: templates/alsijil/class_register/week_view.html:239
+#: templates/alsijil/print/full_register.html:370
 msgid "Homework"
 msgstr ""
 
-#: models.py:129 templates/alsijil/class_register/lesson.html:145
-#: templates/alsijil/class_register/week_view.html:92
-#: templates/alsijil/class_register/week_view.html:189
-#: templates/alsijil/class_register/week_view.html:222
+#: models.py:152 templates/alsijil/class_register/lesson.html:149
+#: templates/alsijil/class_register/week_view.html:108
+#: templates/alsijil/class_register/week_view.html:212
+#: templates/alsijil/class_register/week_view.html:245
 msgid "Group note"
 msgstr ""
 
-#: models.py:171 templates/alsijil/class_register/lesson.html:97
-#: templates/alsijil/class_register/lesson.html:120
+#: models.py:202 templates/alsijil/class_register/lesson.html:101
+#: templates/alsijil/class_register/lesson.html:124
 msgid "Lesson documentation"
 msgstr ""
 
-#: models.py:172 templates/alsijil/class_register/week_view.html:67
+#: models.py:203 templates/alsijil/class_register/week_view.html:68
 msgid "Lesson documentations"
 msgstr ""
 
-#: models.py:200
+#: models.py:231
 msgid "Extra mark"
 msgstr ""
 
-#: models.py:208
+#: models.py:239
 msgid "Can view week overview"
 msgstr ""
 
-#: models.py:209
+#: models.py:240
 msgid "Can register absence"
 msgstr ""
 
-#: models.py:210
+#: models.py:241
 msgid "Can list all personal note filters"
 msgstr ""
 
@@ -262,6 +314,10 @@ msgstr ""
 msgid "Lessons in the past are not affected by this setting, you can open them whenever you want."
 msgstr ""
 
+#: preferences.py:68
+msgid "Allow teachers to add data for lessons in holidays"
+msgstr ""
+
 #: tables.py:16 tables.py:36
 msgid "Edit"
 msgstr ""
@@ -273,13 +329,13 @@ msgstr ""
 #: templates/alsijil/absences/register.html:5
 #: templates/alsijil/absences/register.html:6
 #: templates/alsijil/class_register/person.html:30
-#: templates/alsijil/class_register/week_view.html:256
+#: templates/alsijil/class_register/week_view.html:282
 #: templates/alsijil/partials/persons_with_stats.html:115
 msgid "Register absence"
 msgstr ""
 
 #: templates/alsijil/absences/register.html:9
-#: templates/alsijil/class_register/lesson.html:242
+#: templates/alsijil/class_register/lesson.html:246
 msgid "Person"
 msgstr ""
 
@@ -381,13 +437,12 @@ msgid "My next lesson"
 msgstr ""
 
 #: templates/alsijil/class_register/lesson.html:46
-#: templates/alsijil/class_register/lesson.html:167
+#: templates/alsijil/class_register/lesson.html:171
 #, python-format
 msgid "%(period)s. period"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:77
-#: templates/alsijil/class_register/lesson.html:359
+#: templates/alsijil/class_register/lesson.html:79
 #, python-format
 msgid ""
 "\n"
@@ -395,8 +450,7 @@ msgid ""
 "        "
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:85
-#: templates/alsijil/class_register/lesson.html:367
+#: templates/alsijil/class_register/lesson.html:87
 #, python-format
 msgid ""
 "\n"
@@ -404,40 +458,40 @@ msgid ""
 "        "
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:107
+#: templates/alsijil/class_register/lesson.html:111
 msgid "Previous lesson"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:111
-#: templates/alsijil/class_register/lesson.html:342
+#: templates/alsijil/class_register/lesson.html:115
+#: templates/alsijil/class_register/lesson.html:346
 msgid "Change history"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:166
+#: templates/alsijil/class_register/lesson.html:170
 msgid "Overview: Previous lesson"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:173
+#: templates/alsijil/class_register/lesson.html:177
 msgid "Lesson topic of previous lesson:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:180
+#: templates/alsijil/class_register/lesson.html:184
 msgid "Homework for this lesson:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:187
+#: templates/alsijil/class_register/lesson.html:191
 msgid "Group notes for previous lesson:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:194
+#: templates/alsijil/class_register/lesson.html:198
 msgid "Absent persons:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:201
+#: templates/alsijil/class_register/lesson.html:205
 msgid "Late persons:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:244
+#: templates/alsijil/class_register/lesson.html:248
 #: templates/alsijil/class_register/person.html:110
 #: templates/alsijil/partials/persons_with_stats.html:17
 #: templates/alsijil/partials/persons_with_stats.html:34
@@ -446,10 +500,33 @@ msgstr ""
 msgid "Tardiness"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:267
+#: templates/alsijil/class_register/lesson.html:271
 msgid "Tardiness (in m)"
 msgstr ""
 
+#: templates/alsijil/class_register/lesson.html:364
+#, python-format
+msgid ""
+"\n"
+"            Previous %(subject)s lesson\n"
+"          "
+msgstr ""
+
+#: templates/alsijil/class_register/lesson.html:372
+#, python-format
+msgid ""
+"\n"
+"            Next %(subject)s lesson\n"
+"          "
+msgstr ""
+
+#: templates/alsijil/class_register/lesson.html:387
+msgid ""
+"\n"
+"                This lesson overlaps with holidays and can't be edited.\n"
+"              "
+msgstr ""
+
 #: templates/alsijil/class_register/person.html:8
 msgid "Class register: person"
 msgstr ""
@@ -554,44 +631,44 @@ msgid ""
 "      %(instance)s"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:84
+#: templates/alsijil/class_register/week_view.html:100
 msgid "Period"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:86
+#: templates/alsijil/class_register/week_view.html:102
 msgid "Groups"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:88
-#: templates/alsijil/class_register/week_view.html:163
+#: templates/alsijil/class_register/week_view.html:104
+#: templates/alsijil/class_register/week_view.html:186
 #: templates/alsijil/print/full_register.html:169
 #: templates/alsijil/print/full_register.html:200
 msgid "Subject"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:89
-#: templates/alsijil/class_register/week_view.html:173
+#: templates/alsijil/class_register/week_view.html:105
+#: templates/alsijil/class_register/week_view.html:196
 msgid "Teachers"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:262
+#: templates/alsijil/class_register/week_view.html:288
 msgid "unexcused"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:265
+#: templates/alsijil/class_register/week_view.html:291
 msgid "Summed up tardiness"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:268
+#: templates/alsijil/class_register/week_view.html:294
 #: templates/alsijil/partials/persons_with_stats.html:94
 msgid "Count of tardiness"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:297
+#: templates/alsijil/class_register/week_view.html:323
 msgid "No lessons available"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:300
+#: templates/alsijil/class_register/week_view.html:326
 msgid ""
 "\n"
 "            There are no lessons for the selected group or teacher in this week.\n"
@@ -660,7 +737,7 @@ msgid "Data complete"
 msgstr ""
 
 #: templates/alsijil/partials/lesson_status_icon.html:12
-#: templates/alsijil/print/full_register.html:406
+#: templates/alsijil/print/full_register.html:404
 msgid "Lesson cancelled"
 msgstr ""
 
@@ -677,9 +754,9 @@ msgid "Substitution"
 msgstr ""
 
 #: templates/alsijil/partials/mark_as_buttons.html:4
-#: templates/alsijil/print/full_register.html:335
-#: templates/alsijil/print/full_register.html:424
-#: templates/alsijil/print/full_register.html:439
+#: templates/alsijil/print/full_register.html:334
+#: templates/alsijil/print/full_register.html:422
+#: templates/alsijil/print/full_register.html:437
 msgid "e"
 msgstr ""
 
@@ -835,17 +912,17 @@ msgid "Date"
 msgstr ""
 
 #: templates/alsijil/print/full_register.html:309
-#: templates/alsijil/print/full_register.html:369
+#: templates/alsijil/print/full_register.html:367
 msgid "Pe."
 msgstr ""
 
 #: templates/alsijil/print/full_register.html:310
-#: templates/alsijil/print/full_register.html:370
+#: templates/alsijil/print/full_register.html:368
 msgid "Subj."
 msgstr ""
 
 #: templates/alsijil/print/full_register.html:311
-#: templates/alsijil/print/full_register.html:374
+#: templates/alsijil/print/full_register.html:372
 msgid "Te."
 msgstr ""
 
@@ -853,70 +930,70 @@ msgstr ""
 msgid "Tard."
 msgstr ""
 
-#: templates/alsijil/print/full_register.html:330
+#: templates/alsijil/print/full_register.html:329
 msgid "Yes"
 msgstr ""
 
-#: templates/alsijil/print/full_register.html:363
+#: templates/alsijil/print/full_register.html:361
 msgid "Lesson documentation for week"
 msgstr ""
 
-#: templates/alsijil/print/full_register.html:373
+#: templates/alsijil/print/full_register.html:371
 msgid "Notes"
 msgstr ""
 
-#: views.py:65
+#: views.py:68
 msgid "You either selected an invalid lesson or there is currently no lesson in progress."
 msgstr ""
 
-#: views.py:90
+#: views.py:93
 msgid "You are not allowed to create a lesson documentation for a lesson in the future."
 msgstr ""
 
-#: views.py:127
+#: views.py:141
 msgid "The lesson documentation has been saved."
 msgstr ""
 
-#: views.py:151
+#: views.py:165
 msgid "The personal notes have been saved."
 msgstr ""
 
-#: views.py:570
+#: views.py:591
 msgid "The absences have been marked as excused."
 msgstr ""
 
-#: views.py:585
+#: views.py:606
 msgid "The absence has been marked as excused."
 msgstr ""
 
-#: views.py:721
+#: views.py:749
 msgid "The absence has been saved."
 msgstr ""
 
-#: views.py:741
+#: views.py:770
 msgid "The personal note has been deleted."
 msgstr ""
 
-#: views.py:762
+#: views.py:792
 msgid "The extra mark has been created."
 msgstr ""
 
-#: views.py:773
+#: views.py:804
 msgid "The extra mark has been saved."
 msgstr ""
 
-#: views.py:783
+#: views.py:815
 msgid "The extra mark has been deleted."
 msgstr ""
 
-#: views.py:803
+#: views.py:836
 msgid "The excuse type has been created."
 msgstr ""
 
-#: views.py:814
+#: views.py:848
 msgid "The excuse type has been saved."
 msgstr ""
 
-#: views.py:824
+#: views.py:859
 msgid "The excuse type has been deleted."
 msgstr ""
diff --git a/aleksis/apps/alsijil/locale/tr_TR/LC_MESSAGES/django.po b/aleksis/apps/alsijil/locale/tr_TR/LC_MESSAGES/django.po
index 219d7af7ff7ca661ccb440d5fab0002ecb546788..4704f58a5eb1586fdaf87d76c815c27f80e81c30 100644
--- a/aleksis/apps/alsijil/locale/tr_TR/LC_MESSAGES/django.po
+++ b/aleksis/apps/alsijil/locale/tr_TR/LC_MESSAGES/django.po
@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2020-12-05 21:26+0100\n"
+"POT-Creation-Date: 2021-01-22 22:01+0100\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -17,11 +17,63 @@ msgstr ""
 "Content-Type: text/plain; charset=UTF-8\n"
 "Content-Transfer-Encoding: 8bit\n"
 
+#: data_checks.py:15
+msgid "Delete object"
+msgstr ""
+
+#: data_checks.py:25
+msgid "Set current groups"
+msgstr ""
+
+#: data_checks.py:36
+msgid "Reset personal note to defaults"
+msgstr ""
+
+#: data_checks.py:48
+msgid "Ensure that there are no personal notes in cancelled lessons"
+msgstr ""
+
+#: data_checks.py:49
+msgid "The personal note is related to a cancelled lesson."
+msgstr ""
+
+#: data_checks.py:72
+msgid "Ensure that 'groups_of_person' is set for every personal note"
+msgstr ""
+
+#: data_checks.py:73
+msgid "The personal note has no group in 'groups_of_person'."
+msgstr ""
+
+#: data_checks.py:107
+msgid "Ensure that there are no filled out lesson documentations on holidays"
+msgstr ""
+
+#: data_checks.py:108
+msgid "The lesson documentation is on holidays."
+msgstr ""
+
+#: data_checks.py:143
+msgid "Ensure that there are no filled out personal notes on holidays"
+msgstr ""
+
+#: data_checks.py:144
+msgid "The personal note is on holidays."
+msgstr ""
+
+#: data_checks.py:174
+msgid "Ensure that there are no excused personal notes without an absence"
+msgstr ""
+
+#: data_checks.py:175
+msgid "The personal note is marked as excused, but not as absent."
+msgstr ""
+
 #: forms.py:29
 msgid "Homework for the next lesson"
 msgstr ""
 
-#: forms.py:54 templates/alsijil/class_register/week_view.html:168
+#: forms.py:54 templates/alsijil/class_register/week_view.html:191
 #: templates/alsijil/print/full_register.html:199
 msgid "Group"
 msgstr ""
@@ -52,16 +104,16 @@ msgid "End period"
 msgstr ""
 
 #: forms.py:130 templates/alsijil/absences/register_confirm.html:52
-#: templates/alsijil/class_register/lesson.html:243
+#: templates/alsijil/class_register/lesson.html:247
 #: templates/alsijil/class_register/person.html:207
-#: templates/alsijil/class_register/week_view.html:261
+#: templates/alsijil/class_register/week_view.html:287
 #: templates/alsijil/print/full_register.html:75
 #: templates/alsijil/print/full_register.html:312
 msgid "Absent"
 msgstr ""
 
 #: forms.py:131 templates/alsijil/absences/register_confirm.html:56
-#: templates/alsijil/class_register/lesson.html:245
+#: templates/alsijil/class_register/lesson.html:249
 #: templates/alsijil/class_register/person.html:98
 #: templates/alsijil/class_register/person.html:215
 #: templates/alsijil/partials/mark_as_buttons.html:2
@@ -72,14 +124,14 @@ msgstr ""
 msgid "Excused"
 msgstr ""
 
-#: forms.py:133 models.py:37 models.py:64
-#: templates/alsijil/class_register/lesson.html:246
-#: templates/alsijil/class_register/lesson.html:281
+#: forms.py:133 models.py:45 models.py:79
+#: templates/alsijil/class_register/lesson.html:250
+#: templates/alsijil/class_register/lesson.html:285
 msgid "Excuse type"
 msgstr ""
 
-#: forms.py:138 templates/alsijil/class_register/lesson.html:248
-#: templates/alsijil/class_register/lesson.html:302
+#: forms.py:138 templates/alsijil/class_register/lesson.html:252
+#: templates/alsijil/class_register/lesson.html:306
 #: templates/alsijil/print/full_register.html:314
 msgid "Remarks"
 msgstr ""
@@ -110,14 +162,14 @@ msgstr ""
 msgid "My students"
 msgstr ""
 
-#: menus.py:71 models.py:38 templates/alsijil/excuse_type/list.html:8
+#: menus.py:71 models.py:46 templates/alsijil/excuse_type/list.html:8
 #: templates/alsijil/excuse_type/list.html:9
 #: templates/alsijil/partials/legend.html:26
 msgid "Excuse types"
 msgstr ""
 
-#: menus.py:82 models.py:70 models.py:201
-#: templates/alsijil/class_register/lesson.html:247
+#: menus.py:82 models.py:84 models.py:232
+#: templates/alsijil/class_register/lesson.html:251
 #: templates/alsijil/extra_mark/list.html:8
 #: templates/alsijil/extra_mark/list.html:9
 #: templates/alsijil/partials/legend.html:41
@@ -162,75 +214,75 @@ msgstr ""
 msgid "Can register an absence for a person"
 msgstr ""
 
-#: models.py:25 models.py:188
+#: models.py:33 models.py:219
 msgid "Short name"
 msgstr ""
 
-#: models.py:26 models.py:189 templates/alsijil/class_register/groups.html:20
+#: models.py:34 models.py:220 templates/alsijil/class_register/groups.html:20
 #: templates/alsijil/partials/persons_with_stats.html:14
 #: templates/alsijil/partials/persons_with_stats.html:24
 msgid "Name"
 msgstr ""
 
-#: models.py:54 models.py:121
+#: models.py:69 models.py:144
 msgid "Year"
 msgstr ""
 
-#: models.py:101
+#: models.py:122
 msgid "Personal note"
 msgstr ""
 
-#: models.py:102 templates/alsijil/class_register/lesson.html:101
-#: templates/alsijil/class_register/lesson.html:233
-#: templates/alsijil/class_register/week_view.html:68
-#: templates/alsijil/class_register/week_view.html:242
+#: models.py:123 templates/alsijil/class_register/lesson.html:105
+#: templates/alsijil/class_register/lesson.html:237
+#: templates/alsijil/class_register/week_view.html:71
+#: templates/alsijil/class_register/week_view.html:267
 msgid "Personal notes"
 msgstr ""
 
-#: models.py:127 templates/alsijil/class_register/lesson.html:129
-#: templates/alsijil/class_register/week_view.html:90
-#: templates/alsijil/class_register/week_view.html:177
-#: templates/alsijil/print/full_register.html:371
+#: models.py:150 templates/alsijil/class_register/lesson.html:133
+#: templates/alsijil/class_register/week_view.html:106
+#: templates/alsijil/class_register/week_view.html:200
+#: templates/alsijil/print/full_register.html:369
 msgid "Lesson topic"
 msgstr ""
 
-#: models.py:128 templates/alsijil/class_register/lesson.html:137
-#: templates/alsijil/class_register/week_view.html:91
-#: templates/alsijil/class_register/week_view.html:183
-#: templates/alsijil/class_register/week_view.html:216
-#: templates/alsijil/print/full_register.html:372
+#: models.py:151 templates/alsijil/class_register/lesson.html:141
+#: templates/alsijil/class_register/week_view.html:107
+#: templates/alsijil/class_register/week_view.html:206
+#: templates/alsijil/class_register/week_view.html:239
+#: templates/alsijil/print/full_register.html:370
 msgid "Homework"
 msgstr ""
 
-#: models.py:129 templates/alsijil/class_register/lesson.html:145
-#: templates/alsijil/class_register/week_view.html:92
-#: templates/alsijil/class_register/week_view.html:189
-#: templates/alsijil/class_register/week_view.html:222
+#: models.py:152 templates/alsijil/class_register/lesson.html:149
+#: templates/alsijil/class_register/week_view.html:108
+#: templates/alsijil/class_register/week_view.html:212
+#: templates/alsijil/class_register/week_view.html:245
 msgid "Group note"
 msgstr ""
 
-#: models.py:171 templates/alsijil/class_register/lesson.html:97
-#: templates/alsijil/class_register/lesson.html:120
+#: models.py:202 templates/alsijil/class_register/lesson.html:101
+#: templates/alsijil/class_register/lesson.html:124
 msgid "Lesson documentation"
 msgstr ""
 
-#: models.py:172 templates/alsijil/class_register/week_view.html:67
+#: models.py:203 templates/alsijil/class_register/week_view.html:68
 msgid "Lesson documentations"
 msgstr ""
 
-#: models.py:200
+#: models.py:231
 msgid "Extra mark"
 msgstr ""
 
-#: models.py:208
+#: models.py:239
 msgid "Can view week overview"
 msgstr ""
 
-#: models.py:209
+#: models.py:240
 msgid "Can register absence"
 msgstr ""
 
-#: models.py:210
+#: models.py:241
 msgid "Can list all personal note filters"
 msgstr ""
 
@@ -262,6 +314,10 @@ msgstr ""
 msgid "Lessons in the past are not affected by this setting, you can open them whenever you want."
 msgstr ""
 
+#: preferences.py:68
+msgid "Allow teachers to add data for lessons in holidays"
+msgstr ""
+
 #: tables.py:16 tables.py:36
 msgid "Edit"
 msgstr ""
@@ -273,13 +329,13 @@ msgstr ""
 #: templates/alsijil/absences/register.html:5
 #: templates/alsijil/absences/register.html:6
 #: templates/alsijil/class_register/person.html:30
-#: templates/alsijil/class_register/week_view.html:256
+#: templates/alsijil/class_register/week_view.html:282
 #: templates/alsijil/partials/persons_with_stats.html:115
 msgid "Register absence"
 msgstr ""
 
 #: templates/alsijil/absences/register.html:9
-#: templates/alsijil/class_register/lesson.html:242
+#: templates/alsijil/class_register/lesson.html:246
 msgid "Person"
 msgstr ""
 
@@ -381,13 +437,12 @@ msgid "My next lesson"
 msgstr ""
 
 #: templates/alsijil/class_register/lesson.html:46
-#: templates/alsijil/class_register/lesson.html:167
+#: templates/alsijil/class_register/lesson.html:171
 #, python-format
 msgid "%(period)s. period"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:77
-#: templates/alsijil/class_register/lesson.html:359
+#: templates/alsijil/class_register/lesson.html:79
 #, python-format
 msgid ""
 "\n"
@@ -395,8 +450,7 @@ msgid ""
 "        "
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:85
-#: templates/alsijil/class_register/lesson.html:367
+#: templates/alsijil/class_register/lesson.html:87
 #, python-format
 msgid ""
 "\n"
@@ -404,40 +458,40 @@ msgid ""
 "        "
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:107
+#: templates/alsijil/class_register/lesson.html:111
 msgid "Previous lesson"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:111
-#: templates/alsijil/class_register/lesson.html:342
+#: templates/alsijil/class_register/lesson.html:115
+#: templates/alsijil/class_register/lesson.html:346
 msgid "Change history"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:166
+#: templates/alsijil/class_register/lesson.html:170
 msgid "Overview: Previous lesson"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:173
+#: templates/alsijil/class_register/lesson.html:177
 msgid "Lesson topic of previous lesson:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:180
+#: templates/alsijil/class_register/lesson.html:184
 msgid "Homework for this lesson:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:187
+#: templates/alsijil/class_register/lesson.html:191
 msgid "Group notes for previous lesson:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:194
+#: templates/alsijil/class_register/lesson.html:198
 msgid "Absent persons:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:201
+#: templates/alsijil/class_register/lesson.html:205
 msgid "Late persons:"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:244
+#: templates/alsijil/class_register/lesson.html:248
 #: templates/alsijil/class_register/person.html:110
 #: templates/alsijil/partials/persons_with_stats.html:17
 #: templates/alsijil/partials/persons_with_stats.html:34
@@ -446,10 +500,33 @@ msgstr ""
 msgid "Tardiness"
 msgstr ""
 
-#: templates/alsijil/class_register/lesson.html:267
+#: templates/alsijil/class_register/lesson.html:271
 msgid "Tardiness (in m)"
 msgstr ""
 
+#: templates/alsijil/class_register/lesson.html:364
+#, python-format
+msgid ""
+"\n"
+"            Previous %(subject)s lesson\n"
+"          "
+msgstr ""
+
+#: templates/alsijil/class_register/lesson.html:372
+#, python-format
+msgid ""
+"\n"
+"            Next %(subject)s lesson\n"
+"          "
+msgstr ""
+
+#: templates/alsijil/class_register/lesson.html:387
+msgid ""
+"\n"
+"                This lesson overlaps with holidays and can't be edited.\n"
+"              "
+msgstr ""
+
 #: templates/alsijil/class_register/person.html:8
 msgid "Class register: person"
 msgstr ""
@@ -554,44 +631,44 @@ msgid ""
 "      %(instance)s"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:84
+#: templates/alsijil/class_register/week_view.html:100
 msgid "Period"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:86
+#: templates/alsijil/class_register/week_view.html:102
 msgid "Groups"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:88
-#: templates/alsijil/class_register/week_view.html:163
+#: templates/alsijil/class_register/week_view.html:104
+#: templates/alsijil/class_register/week_view.html:186
 #: templates/alsijil/print/full_register.html:169
 #: templates/alsijil/print/full_register.html:200
 msgid "Subject"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:89
-#: templates/alsijil/class_register/week_view.html:173
+#: templates/alsijil/class_register/week_view.html:105
+#: templates/alsijil/class_register/week_view.html:196
 msgid "Teachers"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:262
+#: templates/alsijil/class_register/week_view.html:288
 msgid "unexcused"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:265
+#: templates/alsijil/class_register/week_view.html:291
 msgid "Summed up tardiness"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:268
+#: templates/alsijil/class_register/week_view.html:294
 #: templates/alsijil/partials/persons_with_stats.html:94
 msgid "Count of tardiness"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:297
+#: templates/alsijil/class_register/week_view.html:323
 msgid "No lessons available"
 msgstr ""
 
-#: templates/alsijil/class_register/week_view.html:300
+#: templates/alsijil/class_register/week_view.html:326
 msgid ""
 "\n"
 "            There are no lessons for the selected group or teacher in this week.\n"
@@ -660,7 +737,7 @@ msgid "Data complete"
 msgstr ""
 
 #: templates/alsijil/partials/lesson_status_icon.html:12
-#: templates/alsijil/print/full_register.html:406
+#: templates/alsijil/print/full_register.html:404
 msgid "Lesson cancelled"
 msgstr ""
 
@@ -677,9 +754,9 @@ msgid "Substitution"
 msgstr ""
 
 #: templates/alsijil/partials/mark_as_buttons.html:4
-#: templates/alsijil/print/full_register.html:335
-#: templates/alsijil/print/full_register.html:424
-#: templates/alsijil/print/full_register.html:439
+#: templates/alsijil/print/full_register.html:334
+#: templates/alsijil/print/full_register.html:422
+#: templates/alsijil/print/full_register.html:437
 msgid "e"
 msgstr ""
 
@@ -835,17 +912,17 @@ msgid "Date"
 msgstr ""
 
 #: templates/alsijil/print/full_register.html:309
-#: templates/alsijil/print/full_register.html:369
+#: templates/alsijil/print/full_register.html:367
 msgid "Pe."
 msgstr ""
 
 #: templates/alsijil/print/full_register.html:310
-#: templates/alsijil/print/full_register.html:370
+#: templates/alsijil/print/full_register.html:368
 msgid "Subj."
 msgstr ""
 
 #: templates/alsijil/print/full_register.html:311
-#: templates/alsijil/print/full_register.html:374
+#: templates/alsijil/print/full_register.html:372
 msgid "Te."
 msgstr ""
 
@@ -853,70 +930,70 @@ msgstr ""
 msgid "Tard."
 msgstr ""
 
-#: templates/alsijil/print/full_register.html:330
+#: templates/alsijil/print/full_register.html:329
 msgid "Yes"
 msgstr ""
 
-#: templates/alsijil/print/full_register.html:363
+#: templates/alsijil/print/full_register.html:361
 msgid "Lesson documentation for week"
 msgstr ""
 
-#: templates/alsijil/print/full_register.html:373
+#: templates/alsijil/print/full_register.html:371
 msgid "Notes"
 msgstr ""
 
-#: views.py:65
+#: views.py:68
 msgid "You either selected an invalid lesson or there is currently no lesson in progress."
 msgstr ""
 
-#: views.py:90
+#: views.py:93
 msgid "You are not allowed to create a lesson documentation for a lesson in the future."
 msgstr ""
 
-#: views.py:127
+#: views.py:141
 msgid "The lesson documentation has been saved."
 msgstr ""
 
-#: views.py:151
+#: views.py:165
 msgid "The personal notes have been saved."
 msgstr ""
 
-#: views.py:570
+#: views.py:591
 msgid "The absences have been marked as excused."
 msgstr ""
 
-#: views.py:585
+#: views.py:606
 msgid "The absence has been marked as excused."
 msgstr ""
 
-#: views.py:721
+#: views.py:749
 msgid "The absence has been saved."
 msgstr ""
 
-#: views.py:741
+#: views.py:770
 msgid "The personal note has been deleted."
 msgstr ""
 
-#: views.py:762
+#: views.py:792
 msgid "The extra mark has been created."
 msgstr ""
 
-#: views.py:773
+#: views.py:804
 msgid "The extra mark has been saved."
 msgstr ""
 
-#: views.py:783
+#: views.py:815
 msgid "The extra mark has been deleted."
 msgstr ""
 
-#: views.py:803
+#: views.py:836
 msgid "The excuse type has been created."
 msgstr ""
 
-#: views.py:814
+#: views.py:848
 msgid "The excuse type has been saved."
 msgstr ""
 
-#: views.py:824
+#: views.py:859
 msgid "The excuse type has been deleted."
 msgstr ""