Time Zone Lookup by Lat/Lon

Description

This is a library for timezone lookup by latitude and longitude. It uses a bounding box to check the most likely polygons with a more accurate winding number algorithm. We need both speed and highly accurate results and this is the resulting project.

Goals of this project?

1. Speed
2. Accuracy.
3. Easy.
4. Concurrent safe.
5. Easy updating of zip file locally.

Simple

1. Grab the tz library.

    go get github.com/catmullet/tz

2. Update the geo json data from evansiroky/timezone-boundary-builder*. (Likely not necessary.)

    make updategeo

*The script will delete the current tzdata.snappy compiled TimeZone file and Download a new geojson zip file. This new geojson file will be loaded and compiled on the next run or by running unit tests. A new tzdata.snappy file will be created.

3. Copy tzdata.snappy

Copy the tzdata.snappy file to the package you are going to initialize the time zone lookup object.

4. Initialize the GeoJson Time Zone Lookup.

    lookup, err := tz.NewGeoJsonTimeZoneLookup("timezones-with-oceans.geojson.zip")
    // OR
    // export GEO_JSON_FILE="path/timezones-with-oceans.geojson.zip" or will pull from root directory
    lookup, err := tz.NewGeoJsonTimeZoneLookup("")
    // OR Get info from logging
    lookup, err := tz.NewGeoJsonTimeZoneLookup("", os.Stderr)

5. Parse

Parse by Lat Lon and return string value of time zone.

    timeZone := lookup.TimeZone(5.261417, -3.925778)

Parse for time.Location.

    var ti = time.Now()
    
    var loc, _ = lookup.Location(5.261417, -3.925778)
    
    // Set time to location from lookup, easy!
    ti.In(loc).Zone()

Benchmarks

Tests performed with cpu: Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz

Test	Operations Ran	ns per operation
BenchmarkTimeZone/coordinates_5.261417_-3.925778-12	109633 op	9837 ns/op
BenchmarkTimeZone/coordinates_-15.678889_34.973889-12	41721 op	27305 ns/op
BenchmarkTimeZone/coordinates_-12.65945_18.25674-12	74956 op	17318 ns/op
BenchmarkTimeZone/coordinates_41.8976_-87.6205-12	59955 op	19741 ns/op
BenchmarkTimeZone/coordinates_47.6897_-122.4023-12	65709 op	17656 ns/op
BenchmarkTimeZone/coordinates_42.7235_-73.6931-12	98896 op	12355 ns/op
BenchmarkTimeZone/coordinates_42.5807_-83.0223-12	98629 op	10762 ns/op
BenchmarkTimeZone/coordinates_36.8381_-84.85-12	37291 op	31924 ns/op
BenchmarkTimeZone/coordinates_40.1674_-85.3583-12	57832 op	19866 ns/op
BenchmarkTimeZone/coordinates_37.9643_-86.7453-12	61338 op	19274 ns/op
BenchmarkTimeZone/coordinates_38.6043_-90.2417-12	61954 op	20196 ns/op
BenchmarkTimeZone/coordinates_41.1591_-104.8261-12	86883 op	14256 ns/op
BenchmarkTimeZone/coordinates_35.1991_-111.6348-12	61996 op	18842 ns/op
BenchmarkTimeZone/coordinates_43.1432_-115.675-12	50565 op	24131 ns/op
BenchmarkTimeZone/coordinates_47.5886_-122.3382-12	68821 op	18421 ns/op
BenchmarkTimeZone/coordinates_58.3168_-134.4397-12	93099 op	13280 ns/op
BenchmarkTimeZone/coordinates_21.4381_-158.0493-12	12163994 op	96.95 ns/op
BenchmarkTimeZone/coordinates_42.7_-80-12	135962 op	8506 ns/op
BenchmarkTimeZone/coordinates_51.0036_-114.0161-12	323289 op	3779 ns/op
BenchmarkTimeZone/coordinates_-16.4965_-68.1702-12	64844 op	18756 ns/op
BenchmarkTimeZone/coordinates_-31.9369_115.8453-12	275347 op	4256 ns/op
BenchmarkTimeZone/coordinates_42_-87.5-12	63606 op	19925 ns/op
BenchmarkTimeZone/coordinates_41.8976_-87.6205#01-12	63562 op	19546 ns/op
BenchmarkTimeZone/coordinates_47.6897_-122.4023#01-12	70030 op	17950 ns/op
BenchmarkTimeZone/coordinates_42.7235_-73.6931#01-12	96730 op	12206 ns/op
BenchmarkTimeZone/coordinates_42.5807_-83.0223#01-12	112562 op	10770 ns/op
BenchmarkTimeZone/coordinates_36.8381_-84.85#01-12	38658 op	33090 ns/op
BenchmarkTimeZone/coordinates_40.1674_-85.3583#01-12	58844 op	20873 ns/op
BenchmarkTimeZone/coordinates_37.9643_-86.7453#01-12	61153 op	20413 ns/op
BenchmarkTimeZone/coordinates_38.6043_-90.2417#01-12	50996 op	21369 ns/op
BenchmarkTimeZone/coordinates_41.1591_-104.8261#01-12	76140 op	15558 ns/op
BenchmarkTimeZone/coordinates_35.1991_-111.6348#01-12	60016 op	19801 ns/op
BenchmarkTimeZone/coordinates_43.1432_-115.675#01-12	46855 op	25990 ns/op
BenchmarkTimeZone/coordinates_47.5886_-122.3382#01-12	53744 op	23905 ns/op
BenchmarkTimeZone/coordinates_58.3168_-134.4397#01-12	66007 op	16711 ns/op
BenchmarkTimeZone/coordinates_21.4381_-158.0493#01-12	8266512 op	123.8 ns/op
BenchmarkTimeZone/coordinates_42.7_-80#01-12	112492 op	10378 ns/op
BenchmarkTimeZone/coordinates_51.0036_-114.0161#01-12	294398 op	4424 ns/op
BenchmarkTimeZone/coordinates_-16.4965_-68.1702#01-12	60153 op	19283 ns/op
BenchmarkTimeZone/coordinates_-31.9369_115.8453#01-12	263713 op	4694 ns/op
BenchmarkTimeZone/coordinates_42_-87.5#01-12	61891 op	20164 ns/op
BenchmarkTimeZone/coordinates_41.8976_-87.6205#02-12	55926 op	20487 ns/op
BenchmarkTimeZone/coordinates_47.6897_-122.4023#02-12	67516 op	19023 ns/op
BenchmarkTimeZone/coordinates_42.7235_-73.6931#02-12	92011 op	13674 ns/op
BenchmarkTimeZone/coordinates_42.5807_-83.0223#02-12	97562 op	12193 ns/op
BenchmarkTimeZone/coordinates_36.8381_-84.85#02-12	36657 op	32004 ns/op
BenchmarkTimeZone/coordinates_40.1674_-85.3583#02-12	59169 op	20827 ns/op
BenchmarkTimeZone/coordinates_37.9643_-86.7453#02-12	59452 op	20075 ns/op
BenchmarkTimeZone/coordinates_38.6043_-90.2417#02-12	56371 op	19961 ns/op
BenchmarkTimeZone/coordinates_41.1591_-104.8261#02-12	79848 op	14434 ns/op
BenchmarkTimeZone/coordinates_35.1991_-111.6348#02-12	59436 op	18598 ns/op
BenchmarkTimeZone/coordinates_43.1432_-115.675#02-12	49734 op	24137 ns/op
BenchmarkTimeZone/coordinates_47.5886_-122.3382#02-12	66818 op	18188 ns/op
BenchmarkTimeZone/coordinates_58.3168_-134.4397#02-12	94588 op	12781 ns/op
BenchmarkTimeZone/coordinates_21.4381_-158.0493#02-12	12312768 op	99.03 ns/op
BenchmarkTimeZone/coordinates_42.7_-80#02-12	129206 op	8987 ns/op
BenchmarkTimeZone/coordinates_51.0036_-114.0161#02-12	310020 op	4098 ns/op
BenchmarkTimeZone/coordinates_-16.4965_-68.1702#02-12	61988 op	21531 ns/op
BenchmarkTimeZone/coordinates_-31.9369_115.8453#02-12	167610 op	7179 ns/op
BenchmarkTimeZone/coordinates_42_-87.5#02-12	51849 op	20606 ns/op