{-# OPTIONS -Wall -Werror #-} module Data.Time.Calendar.MonthDay ( monthAndDayToDayOfYear,dayOfYearToMonthAndDay,monthLength ) where import Data.Time.Calendar.Private -- | convert month and day in the Gregorian or Julian calendars to day of year. -- First arg is leap year flag monthAndDayToDayOfYear :: Bool -> Int -> Int -> Int monthAndDayToDayOfYear isLeap month day = (div (367 * month'' - 362) 12) + k + day' where month' = clip 1 12 month day' = fromIntegral (clip 1 (monthLength' isLeap month') day) month'' = fromIntegral month' k = if month' <= 2 then 0 else if isLeap then -1 else -2 -- | convert day of year in the Gregorian or Julian calendars to month and day. -- First arg is leap year flag dayOfYearToMonthAndDay :: Bool -> Int -> (Int,Int) dayOfYearToMonthAndDay isLeap yd = findMonthDay (monthLengths isLeap) (clip 1 (if isLeap then 366 else 365) yd) findMonthDay :: [Int] -> Int -> (Int,Int) findMonthDay (n:ns) yd | yd > n = (\(m,d) -> (m + 1,d)) (findMonthDay ns (yd - n)) findMonthDay _ yd = (1,yd) -- | the length of a given month in the Gregorian or Julian calendars. -- First arg is leap year flag monthLength :: Bool -> Int -> Int monthLength isLeap month' = monthLength' isLeap (clip 1 12 month') monthLength' :: Bool -> Int -> Int monthLength' isLeap month' = (monthLengths isLeap) !! (month' - 1) monthLengths :: Bool -> [Int] monthLengths isleap = [31,if isleap then 29 else 28,31,30,31,30,31,31,30,31,30,31] --J F M A M J J A S O N D