addMonths method
override
This mixin's implementation of Every.next and Every.previous.
Implementation
@override
DateTime addMonths(DateTime date, int months) {
if (months == 0) return startDate(date);
if (months.isNegative) {
if (months == -1) return previous(date);
return previous(addMonths(date, months + 1));
}
return next(addMonths(date, months - 1));
}