isSameMonth method
Returns true if the two DateTime objects have the same month and year, or are both null.
Implementation
@override
bool isSameMonth(DateTime? dateA, DateTime? dateB) {
if (dateA != null) _requireCalendarDate(dateA, 'dateA');
if (dateB != null) _requireCalendarDate(dateB, 'dateB');
return super.isSameMonth(dateA, dateB);
}