-- | ISO 8601 Week Date format module Data.Time.Calendar.WeekDate where import Data.Time.Calendar.OrdinalDate import Data.Time.Calendar.Days import Data.Time.Calendar.Private -- | convert to ISO 8601 Week Date format. First element of result is year, second week number (1-53), third day of week (1 for Monday to 7 for Sunday). -- Note that \"Week\" years are not quite the same as Gregorian years, as the first day of the year is always a Monday. -- The first week of a year is the first week to contain at least four days in the corresponding Gregorian year. toWeekDate :: Day -> (Integer,Int,Int) toWeekDate date@(ModifiedJulianDay mjd) = (y1,fromInteger (w1 + 1),fromInteger (mod d 7) + 1) where (y0,yd) = toOrdinalDate date d = mjd + 2 foo :: Integer -> Integer foo y = bar (toModifiedJulianDay (fromOrdinalDate y 6)) bar k = (div d 7) - (div k 7) w0 = bar (d - (toInteger yd) + 4) (y1,w1) = if w0 == -1 then (y0 - 1,foo (y0 - 1)) else if w0 == 52 then if (foo (y0 + 1)) == 0 then (y0 + 1,0) else (y0,w0) else (y0,w0) -- | convert from ISO 8601 Week Date format. First argument is year, second week number (1-52 or 53), third day of week (1 for Monday to 7 for Sunday). -- Invalid week and day values will be clipped to the correct range. fromWeekDate :: Integer -> Int -> Int -> Day fromWeekDate y w d = ModifiedJulianDay (k - (mod k 7) + (toInteger (((clip 1 (if longYear then 53 else 52) w) * 7) + (clip 1 7 d))) - 10) where k = toModifiedJulianDay (fromOrdinalDate y 6) longYear = case toWeekDate (fromOrdinalDate y 365) of (_,53,_) -> True _ -> False -- | convert from ISO 8601 Week Date format. First argument is year, second week number (1-52 or 53), third day of week (1 for Monday to 7 for Sunday). -- Invalid week and day values will return Nothing. fromWeekDateValid :: Integer -> Int -> Int -> Maybe Day fromWeekDateValid y w d = do d' <- clipValid 1 7 d let longYear = case toWeekDate (fromOrdinalDate y 365) of (_,53,_) -> True _ -> False w' <- clipValid 1 (if longYear then 53 else 52) w let k = toModifiedJulianDay (fromOrdinalDate y 6) return (ModifiedJulianDay (k - (mod k 7) + (toInteger ((w' * 7) + d')) - 10)) -- | show in ISO 8601 Week Date format as yyyy-Www-d (e.g. \"2006-W46-3\"). showWeekDate :: Day -> String showWeekDate date = (show4 (Just '0') y) ++ "-W" ++ (show2 (Just '0') w) ++ "-" ++ (show d) where (y,w,d) = toWeekDate date