dayOfYearToMonthAndDay
    :: Bool -- ^ 'isLeapYear'?
    -> DayOfYear
    -> (Month, DayOfMonth)
dayOfYearToMonthAndDay leap (view (monthDay leap) -> MonthDay m d) = (m, d)
dayOfYearToMonthAndDay
    :: Bool -- ^ 'isLeapYear'?
    -> DayOfYear
    -> (Month, DayOfMonth)
dayOfYearToMonthAndDay leap (view (monthDay leap) -> MonthDay m d) = (m, d)
dayOfYearToMonthAndDay leap (view (monthDay leap) -> MonthDay m d) = (m, d)