Today we will have a short overview of old data-/time-related packages listed as follows:

• old-time
• time-compat
• old-locale
• time-locale-compat ¹

Those modules are very easily to use but have some shortcomings. The old-time(System.Time) has poor supporting on locale and formating and lack functions to manipulate times. And the TimeDiff is not very sueful. The old-locale(System.Locale), however, is not very out-dated.

old-locale

The old-locale package provides module System.Locale allowing to adapt to local conventions. There is just one single structure defined.

The TimeLocale

data TimeLocale = TimeLocale {
        wDays  :: [(String, String)],
        months :: [(String, String)],
        intervals :: [(String, String)],
        amPm   :: (String, String),
        dateTimeFmt, dateFmt,
        timeFmt, time12Fmt :: String
        } ...

The difference bewteen Data.Time.Format.TimeLocale and System.Locale.TimeLocale is very ignorable. The most significant one is that the has knownTimeZones :: [TimeZone] instead of intervals :: [(String, String)].

Extra

The package time-locale-compat is a interface for importing different versions of TimeLocale. If the version of time is greater then 1.5.0, it will import Data.Time.Format and import System.Locale for otherwise.

old-time

The old-time package provide the System.Time module that contains three distinct structures for representing times:

The ClockTime

The first one is used to represent raw system time in two integers.

data ClockTime = TOD Integer Integer

One can extract system clock time by using

getClockTime :: IO ClockTime

Besides ClockTime there is also a structure for recording differenct between two clock times

data TimeDiff
 = TimeDiff	{
       tdYear    :: Int
     , tdMonth   :: Int
     , tdDay     :: Int 
     , ...
 }

The CalendarTime

The second structure in this module is CalendarTime which will store time in a human-friendly structure:

data CalendarTime
 = CalendarTime  {
       ctYear    :: Int
     , ctMonth   :: Month
     , ctDay     :: Int 
     , ...
 }

Also, this module defines several converting function between CalendarTime, ClockTime and String. Read old-time for more details.

Extra

There is a tiny package, time-compat, providing single typeclass ToUTCTime that define a function toUTCTime to convert an old-time structure to a Data.Time.UTCTime.