module Data.Time.Calendar.JulianYearDay (
module Data.Time.Calendar.JulianYearDay,
) where
import Data.Time.Calendar.Days
import Data.Time.Calendar.Private
import Data.Time.Calendar.Types
toJulianYearAndDay :: Day -> (Year, DayOfYear)
toJulianYearAndDay (ModifiedJulianDay mjd) = (year, yd)
where
a = mjd + 678577
quad = div a 1461
d = mod a 1461
y = min (div d 365) 3
yd = fromInteger (d (y * 365) + 1)
year = quad * 4 + y + 1
fromJulianYearAndDay :: Year -> DayOfYear -> Day
fromJulianYearAndDay year day = ModifiedJulianDay mjd
where
y = year 1
mjd =
( fromIntegral
( clip
1
( if isJulianLeapYear year
then 366
else 365
)
day
)
)
+ (365 * y)
+ (div y 4)
678578
fromJulianYearAndDayValid :: Year -> DayOfYear -> Maybe Day
fromJulianYearAndDayValid year day = do
day' <-
clipValid
1
( if isJulianLeapYear year
then 366
else 365
)
day
let
y = year 1
mjd = (fromIntegral day') + (365 * y) + (div y 4) 678578
return (ModifiedJulianDay mjd)
showJulianYearAndDay :: Day -> String
showJulianYearAndDay date = (show4 y) ++ "-" ++ (show3 d)
where
(y, d) = toJulianYearAndDay date
isJulianLeapYear :: Year -> Bool
isJulianLeapYear year = (mod year 4 == 0)