photoprism / go-tz

Go library for fast offline timezone lookup by latitude and longitude.

gopkg.in/photoprism/go-tz.v2

Go library for fast offline timezone lookup by latitude and longitude. This is a fork of ugjka/go-tz that includes the latest timezone boundaries data and a Makefile for build automation.

Uses a simplified shapefile from timezone-boundary-builder for the lookups. The GeoJSON simplification was done with mapshaper.

Usage Example

import "gopkg.in/photoprism/go-tz.v2/tz"

func TimeZone(lat, lng float64) (result string) {
    result = "UTC"

    zones, err := tz.GetZone(tz.Point{Lat: lat, Lon: lng})

    if err == nil && len(zones) > 0 {
        result = zones[0]
    }

    return result
}

Key Features

• Fast sub-millisecond lookups, even on old hardware
• Timezone shapefile for lookups is embedded in the build binary
• Supports overlapping timezones
• You can load your own geojson shapefile if you want

Known Issues

• The shapefile is simplified using a lossy method, so it may be inaccurate along the boundaries
• Since the library runs completely in memory, it requires about 50 MB of RAM

Licensing

The embedded timezone data is licensed under the Open Data Commons Open Database License (ODbL). Any other code in this library can be used under the terms of the MIT License.

go-tz's Issues

Upstream changes

https://github.com/ugjka/go-tz/releases/tag/v2.2.2