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.
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
>>> tz <- lookupTimeZoneNameFromFile "./test/tz_db/timezone21.bin" 40.7831 (-73.9712) "America/New_York"
LocalTime to UTCTime conversion
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
>>> 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
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.
*Note that all licence references and agreements mentioned in the timezone-detect README section above are relevant to that project's source code only.