monthAndDayToDayOfYearValid
    :: Bool -- ^ 'isLeapYear'?
    -> Month
    -> DayOfMonth
    -> Maybe DayOfYear
monthAndDayToDayOfYearValid leap m d = monthDayValid leap (MonthDay m d)
monthAndDayToDayOfYearValid
    :: Bool -- ^ 'isLeapYear'?
    -> Month
    -> DayOfMonth
    -> Maybe DayOfYear
monthAndDayToDayOfYearValid leap m d = monthDayValid leap (MonthDay m d)
monthAndDayToDayOfYearValid leap m d = monthDayValid leap (MonthDay m d)