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geolocationtimezonelatitude-longitude

How to get a time zone from a location using latitude and longitude coordinates?

Given the latitude and longitude of a location, how does one know what time zone is in effect in that location?

In most cases, we are looking for an IANA/Olson time zone id, although some services may return just a UTC offset, or some other time zone identifier. Please read the timezone tag info for details.

Solution

  • Time Zone Location Web Services

    Raw Time Zone Boundary Data

    • Timezone Boundary Builder - builds time zone shapefiles from OpenStreetMaps map data. Includes territorial waters near coastlines.

    The following projects have previously been sources of time zone boundary data, but are no longer actively maintained.

    Time Zone Geolocation Offline Implementations

    Implementations that use the Timezone Boundary Builder data

    Implementations that use the older tz_world data

    Implementations with its own data

    Libraries that call one of the web services

    • timezone - Ruby gem that calls GeoNames
    • AskGeo has its own libraries for calling from Java or .Net
    • GeoNames has client libraries for just about everything

    Self-hosted web services

    Other Ideas

    Please update this list if you know of any others

    Also, note that the nearest-city approach may not yield the "correct" result, just an approximation.

    Conversion To Windows Zones

    Most of the methods listed will return an IANA time zone id. If you need to convert to a Windows time zone for use with the TimeZoneInfo class in .NET, use the TimeZoneConverter library.

    Don't use zone.tab

    The tz database includes a file called zone.tab. This file is primarily used to present a list of time zones for a user to pick from. It includes the latitude and longitude coordinates for the point of reference for each time zone. This allows a map to be created highlighting these points. For example, see the interactive map shown on the moment-timezone home page.

    While it may be tempting to use this data to resolve the time zone from a latitude and longitude coordinates, consider that these are points - not boundaries. The best one could do would be to determine the closest point, which in many cases will not be the correct point.

    Consider the following example:

                                Time Zone Example Art

    The two squares represent different time zones, where the black dot in each square is the reference location, such as what can be found in zone.tab. The blue dot represents the location we are attempting to find a time zone for. Clearly, this location is within the orange zone on the left, but if we just look at closest distance to the reference point, it will resolve to the greenish zone on the right.