TimezoneDetect

Haskell bindings to the excellent ZoneDetect library, plus additional UNIX-aware facilities to determine the UTC time of a given local time in a latitude and longitude.

Usage

You'll need timezone database files to work with this library, see instructions in the original repository.

Once you have those files in hand, you'll be able to get a timezone from a given latitude and longitude:

>>> lookupTimeZoneName "./test/tz_db/timezone21.bin" 40.7831 (-73.9712) :: Maybe TimeZoneName
Just "America/New_York"

Additionally, we now depend on the timezone-series and timezone-olson packages to add awareness of tz database information.

With that, you can look up the UTC time at a point in time and space:

>>> import Data.Time
>>> localWinter <- parseTimeM True defaultTimeLocale "%Y-%-m-%-d %T" "2019-12-25 00:30:00"
>>> utcTime <- timeAtPointToUTC "./test/tz_db/timezone21.bin" 40.7831 (-73.9712) localWinter
2019-12-25 05:30:00 UTC

>>> localSummer <- parseTimeM True defaultTimeLocale "%Y-%-m-%-d %T" "2019-07-25 00:30:00"
>>> utcTime <- timeAtPointToUTC "./test/tz_db/timezone21.bin" 40.7831 (-73.9712) localWinter
2019-07-25 04:30:00 UTC

You can also opt to obtain the timezone name separately (if you wanted to isolate that as a failure scenario,) and, once in possession of it, use timeInTimeZoneToUTC:

>>> localSummer <- parseTimeM True defaultTimeLocale "%Y-%-m-%-d %T" "2019-07-25 00:30:00"
>>> utcTime <- timeInTimeZoneToUTC "America/New_York" localSummer
2019-07-25 04:30:00 UTC