next method
Returns the next instance of the given date considering this Every
base process.
If the date is a DateTime that matches the Every pattern, a new
DateTime will be generated.
Implementation
@override
DateTime next(DateTime date) {
if (date.day < dueDay) {
return _monthsDay(date, monthDelta: 0);
} else {
return _monthsDay(date, monthDelta: 1);
}
}