Data.Time.Clock

Safe Haskell	Safe
Language	Haskell2010

Universal Time

Time as measured by the earth.

newtype UniversalTime Source

The Modified Julian Date is the day with the fraction of the day, measured from UT midnight. It's used to represent UT1, which is time as measured by the earth's rotation, adjusted for various wobbles.

Absolute intervals

data DiffTime Source

This is a length of time, as measured by a clock. Conversion functions will treat it as seconds. It has a precision of 10^-12 s.

secondsToDiffTime :: Integer -> DiffTime Source

Create a DiffTime which represents an integral number of seconds.

picosecondsToDiffTime :: Integer -> DiffTime Source

Create a DiffTime from a number of picoseconds.

UTC

UTC is time as measured by a clock, corrected to keep pace with the earth by adding or removing occasional seconds, known as "leap seconds". These corrections are not predictable and are announced with six month's notice. No table of these corrections is provided, as any program compiled with it would become out of date in six months.

If you don't care about leap seconds, use UTCTime and NominalDiffTime for your clock calculations, and you'll be fine.

data UTCTime Source

This is the simplest representation of UTC. It consists of the day number, and a time offset from midnight. Note that if a day has a leap second added to it, it will have 86401 seconds.

data NominalDiffTime Source

This is a length of time, as measured by UTC. Conversion functions will treat it as seconds. It has a precision of 10^-12 s. It ignores leap-seconds, so it's not necessarily a fixed amount of clock time. For instance, 23:00 UTC + 2 hours of NominalDiffTime = 01:00 UTC (+ 1 day), regardless of whether a leap-second intervened.

addUTCTime :: NominalDiffTime -> UTCTime -> UTCTime Source

addUTCTime a b = a + b

diffUTCTime :: UTCTime -> UTCTime -> NominalDiffTime Source

diffUTCTime a b = a - b

getCurrentTime :: IO UTCTime Source

Get the current UTC time from the system clock.