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I have a mapping app in which I need to display the borders between U.S. time zones. The easiest and most accurate way would be to feed in a list of lat/long coordinates representing the vertices of these borders, and "connect the dots".

So, the question, simply put, is whether a publicly-available, free database of these geocodes exists, and where?

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A shapefile of the TZ timezones of the United States

Last data update: September 30, 2012

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The tz_us shapefile captures the boundaries of the TZ timezones of the United States, as of TZ 2012c.

The geometries are entirely derived from the countyp020p and timeznp020 shapefiles provided by the National Atlas.

All the TZ timezones of United States listed in TZ’s zone.tab are represented, except for America/Shiprock which is included in America/Denver.

http://efele.net/maps/tz/us/

Shapefile Zipped (Direct Link) http://efele.net/maps/tz/us/tz_us.zip

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  • FYI for people running across this in modern years: EFELE's page hasn't been updated since July 2013. Its source-of-truth was retired in 2014, and that source's successor seems to have retired the TZ updates in 2015. The EFELE site recommends new visitors use this dataset instead, but note that the latter is just an OpenStreetMaps redistributor, not harvesting source-of-truth data itself Jan 27, 2023 at 23:20
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There is a new source of timezone maps as shapefile or geojson at https://github.com/evansiroky/timezone-boundary-builder. The data from that project is sourced from Open Street Map.

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I haven't looked at the data, but check out this USGS version. There's some other information on this page. I have a feeling that the data isn't reflecting some of the local changes like Arizona not switching to daylight savings time.

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This is likely too late for your needs, but http://OnTimeZone.com has what you are looking for. It is more current, more detailed, and more accurate than the efele.net data. It also has data about local deviations from official time zone observance.

The data is available for download in multiple formats and is free for non-commercial, non-governmental use.

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You can download all the US-specific timezone maps in geoJson & KML formats here: https://cartographyvectors.com/search?q=timezone

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OpenHistoricalMap has complete coverage of U.S. standard time zone boundaries as multipolygons, including every official change to the boundaries since the federal system of timekeeping began in 1919. This documentation explains the difference in methodology between OpenHistoricalMap, OpenStreetMap, and the tz database when it comes to U.S. time zones and their boundaries – each database caters to different use cases. The standard tools for querying data in OSM also available for OHM.

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