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{-# LANGUAGE Safe #-}
{-# OPTIONS -fno-warn-orphans #-}
module Data.Time.LocalTime.Internal.LocalTime (
-- * Local Time
LocalTime (..),
addLocalTime,
diffLocalTime,
-- converting UTC and UT1 times to LocalTime
utcToLocalTime,
localTimeToUTC,
ut1ToLocalTime,
localTimeToUT1,
) where
import Control.DeepSeq
import Data.Data
import Data.Time.Calendar.Days
import Data.Time.Calendar.Gregorian
import Data.Time.Clock.Internal.NominalDiffTime
import Data.Time.Clock.Internal.UTCDiff
import Data.Time.Clock.Internal.UTCTime
import Data.Time.Clock.Internal.UniversalTime
import Data.Time.LocalTime.Internal.TimeOfDay
import Data.Time.LocalTime.Internal.TimeZone
-- | A simple day and time aggregate, where the day is of the specified parameter,
-- and the time is a TimeOfDay.
-- Conversion of this (as local civil time) to UTC depends on the time zone.
-- Conversion of this (as local mean time) to UT1 depends on the longitude.
data LocalTime = LocalTime
{ localDay :: Day
, localTimeOfDay :: TimeOfDay
}
deriving (Eq, Ord, Data, Typeable)
instance NFData LocalTime where
rnf (LocalTime d t) = rnf d `seq` rnf t `seq` ()
instance Show LocalTime where
show (LocalTime d t) = (showGregorian d) ++ " " ++ (show t)
-- | addLocalTime a b = a + b
addLocalTime :: NominalDiffTime -> LocalTime -> LocalTime
addLocalTime x = utcToLocalTime utc . addUTCTime x . localTimeToUTC utc
-- | diffLocalTime a b = a - b
diffLocalTime :: LocalTime -> LocalTime -> NominalDiffTime
diffLocalTime a b = diffUTCTime (localTimeToUTC utc a) (localTimeToUTC utc b)
-- | Get the local time of a UTC time in a time zone.
utcToLocalTime :: TimeZone -> UTCTime -> LocalTime
utcToLocalTime tz (UTCTime day dt) = LocalTime (addDays i day) tod
where
(i, tod) = utcToLocalTimeOfDay tz (timeToTimeOfDay dt)
-- | Get the UTC time of a local time in a time zone.
localTimeToUTC :: TimeZone -> LocalTime -> UTCTime
localTimeToUTC tz (LocalTime day tod) = UTCTime (addDays i day) (timeOfDayToTime todUTC)
where
(i, todUTC) = localToUTCTimeOfDay tz tod
-- | Get the local time of a UT1 time on a particular meridian (in degrees, positive is East).
ut1ToLocalTime :: Rational -> UniversalTime -> LocalTime
ut1ToLocalTime long (ModJulianDate date) =
LocalTime (ModifiedJulianDay localMJD) (dayFractionToTimeOfDay localToDOffset)
where
localTime = date + long / 360 :: Rational
localMJD = floor localTime
localToDOffset = localTime - (fromIntegral localMJD)
-- | Get the UT1 time of a local time on a particular meridian (in degrees, positive is East).
localTimeToUT1 :: Rational -> LocalTime -> UniversalTime
localTimeToUT1 long (LocalTime (ModifiedJulianDay localMJD) tod) =
ModJulianDate ((fromIntegral localMJD) + (timeOfDayToDayFraction tod) - (long / 360))
-- orphan instance
instance Show UniversalTime where
show t = show (ut1ToLocalTime 0 t)
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