Haskell bindings for the zone-detect C library; plus tz-aware utils.

Please see the README on GitHub at https://github.com/lfborjas/timezone-detect#readme

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. A copy is provided in the test directory of this repository, but it's intentionally not bundled in the package. We make no guarantees of its correctness, we recommend you use the original authors' files!

Timezone Name Lookup

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

>>> db <- openTimeZoneDatabase "./test/tz_db/timezone21.bin" 
>>> let tz = lookupTimeZoneName db 40.7831 (-73.9712) :: Maybe TimeZoneName
Just "America/New_York"
>>> closeTimeZoneDatabase db

You can use withTimeZoneDatabase to "bracket" access to the file (take care of opening and closing,) but if all you want to do is do a one-off lookup, a convenience function that opens and closes the file when done is also provided, specialized to IO:

>>> tz <- lookupTimeZoneNameFromFile "./test/tz_db/timezone21.bin" 40.7831 (-73.9712)
"America/New_York"

LocalTime to UTCTime conversion

Additionally, we 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
>> db <- openTimeZoneDatabase "./test/tz_db/timezone21.bin"
>>> localWinter <- parseTimeM True defaultTimeLocale "%Y-%-m-%-d %T" "2019-12-25 00:30:00"
>>> utcTime <- timeAtPointToUTC db 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 db 40.7831 (-73.9712) localWinter
2019-07-25 04:30:00 UTC
>>> closeTimeZoneDatabase db

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

Copyright

This library is released under the GPL v2; but the license for the underlying C library bears the following copyright:

Copyright (c) 2018, Bertold Van den Bergh ([email protected]) All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
• Neither the name of the author nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.