Data/Time/LocalTime/LocalTime.hs

    {-# OPTIONS -fno-warn-orphans -fno-warn-unused-imports #-}
    #include "HsConfigure.h"

    -- #hide
    module Data.Time.LocalTime.LocalTime
    (
    	-- * Local Time
    	LocalTime(..),

    	-- converting UTC and UT1 times to LocalTime
    	utcToLocalTime,localTimeToUTC,ut1ToLocalTime,localTimeToUT1,

    	ZonedTime(..),utcToZonedTime,zonedTimeToUTC,getZonedTime,utcToLocalZonedTime
    ) where

    import Data.Time.LocalTime.TimeOfDay
    import Data.Time.LocalTime.TimeZone
    import Data.Time.Calendar
    import Data.Time.Clock
    import Control.DeepSeq
    import Data.Typeable
    #if LANGUAGE_Rank2Types
    import Data.Data
    #endif

    -- | 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
    #if LANGUAGE_DeriveDataTypeable
    #if LANGUAGE_Rank2Types
    #if HAS_DataPico
        ,Data, Typeable
    #endif
    #endif
    #endif
        )

    instance NFData LocalTime where
    	rnf (LocalTime d t) = d `deepseq` t `deepseq` ()

    instance Show LocalTime where
    	show (LocalTime d t) = (showGregorian d) ++ " " ++ (show t)

    -- | show a UTC time in a given time zone as a LocalTime
    utcToLocalTime :: TimeZone -> UTCTime -> LocalTime
    utcToLocalTime tz (UTCTime day dt) = LocalTime (addDays i day) tod where
    	(i,tod) = utcToLocalTimeOfDay tz (timeToTimeOfDay dt)

    -- | find out what UTC time a given LocalTime in a given time zone is
    localTimeToUTC :: TimeZone -> LocalTime -> UTCTime
    localTimeToUTC tz (LocalTime day tod) = UTCTime (addDays i day) (timeOfDayToTime todUTC) where
    	(i,todUTC) = localToUTCTimeOfDay tz tod

    -- | 1st arg is observation 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)

    -- | 1st arg is observation meridian in degrees, positive is East
    localTimeToUT1 :: Rational -> LocalTime -> UniversalTime
    localTimeToUT1 long (LocalTime (ModifiedJulianDay localMJD) tod) = ModJulianDate ((fromIntegral localMJD) + (timeOfDayToDayFraction tod) - (long / 360))

    -- | A local time together with a TimeZone.
    data ZonedTime = ZonedTime {
    	zonedTimeToLocalTime :: LocalTime,
    	zonedTimeZone :: TimeZone
    }
    #if LANGUAGE_DeriveDataTypeable
    #if LANGUAGE_Rank2Types
    #if HAS_DataPico
        deriving (Data, Typeable)
    #endif
    #endif
    #endif

    instance NFData ZonedTime where
    	rnf (ZonedTime lt z) = lt `deepseq` z `deepseq` ()

    utcToZonedTime :: TimeZone -> UTCTime -> ZonedTime
    utcToZonedTime zone time = ZonedTime (utcToLocalTime zone time) zone

    zonedTimeToUTC :: ZonedTime -> UTCTime
    zonedTimeToUTC (ZonedTime t zone) = localTimeToUTC zone t

    instance Show ZonedTime where
    	show (ZonedTime t zone) = show t ++ " " ++ show zone

    -- orphan instance
    instance Show UTCTime where
    	show t = show (utcToZonedTime utc t)

    getZonedTime :: IO ZonedTime
    getZonedTime = do
    	t <- getCurrentTime
    	zone <- getTimeZone t
    	return (utcToZonedTime zone t)

    -- |
    utcToLocalZonedTime :: UTCTime -> IO ZonedTime
    utcToLocalZonedTime t = do
    	zone <- getTimeZone t
    	return (utcToZonedTime zone t)