Resolve "Problems with dates which are in the new year, but in the last calendar week of the old year"

Closes #5 (closed)

calendarweek/calendarweek.py

@@ -69,7 +69,7 @@ class CalendarWeek:
         if when.month == 12 and week == 1:
             year += 1
 
-        if (when.month == 52 or when.month == 53) and when.month == 1:
+        if (week == 52 or week == 53) and when.month == 1:
             year -= 1
 
         return cls(year=year, week=week)