In article
There are just a few functions that a lot of people need, and they are:
These can all be done easily if you use UTCTime for epoch time.
(C functions in parens)
* Convert epoch time to a printable string (ctime)
ctime :: UTCTime -> String ctime t = show (utcToLocalTime utc t) TODO: add a "Show UTCTime" instance, allowing ctime = show
* Convert epoch time to something like struct tm (localtime/gmtime)
gmtime :: UTCTime -> ZonedTime gmtime = zonedTimeFromUTC utc TODO: rename zonedTimeFromUTC to utcToZonedTime. Depending on exactly what you want it to do, localtime is one of these: -- use time zone at given time localtime :: UTCTime -> IO ZonedTime localtime = utcToLocalZonedTime -- use time zone at current time localtime' :: UTCTime -> IO ZonedTime localtime' t = do zone <- getCurrentTimeZone zonedTimeFromUTC zone t The current time zone is different at different times according to the summertime rule. It's possible to find out what it is for a given time.
* Convert a struct tm to epoch time (mktime)
mktime :: ZonedTime -> UTCTime mktime = ztUTC TODO: rename ztUTC to something more sensible.
* Convert a struct tm to a printable string (asctime)
asctime = ZonedTime -> String asctime = show
* Get the current time in epoch seconds (time)
time :: IO UTCTime time = getCurrentTime
For many programmers, myself included, the Unix epoch is the most common, pervasive, and useful way to work with time. Calculations are simple (no need for various TimeDiff sort of things -- just add on x number of seconds), and it is used *everywhere* in the OS, databases, etc. Something that is based on that, such as the C API, is a plus, IMHO.
Simon Marlow seems to be generally of the opinion that POSIX time is evil and should be expunged (because it's a broken representation of UTC). I do however have a few POSIX functions exposed. My UTCTime is more or less the simplest correct representation (consisting of a day count and a time offset). I think UTCTime should remain the main representation of UTC time, but perhaps there should be another module (Data.Time.POSIX) for people who need to muck about with seconds since epoch. It would have POSIXTime with arithmetic, conversion to UTCTime, and getting the current time. Thanks... -- Ashley Yakeley, Seattle WA