Get the full name of your local time zone (OS setting)

Works on windows, linux and macos

Why?

built-in functionality sometimes won't suffice:

zone, _ := time.Now().Zone() // my time zone
fmt.Println(zone) // e.g. "CEST"

loc, err := time.LoadLocation(zone)
if err != nil {
    // the program panics here:
    panic("fail: could not load location from zone")
}

// unreachable:
fmt.Println("success: location loaded from zone")

localizing a date with obtained loc will cause an error because it's not in the IANA format.

panic: time: missing Location in call to Date

While tzlocal gives the correct IANA name

tzname, _ := tzlocal.RuntimeTZ() // assuming error is handled
fmt.Printf("Actual IANA name: %v\n", tzname) // Prints "Actual IANA name: Europe/Paris"

---

Package Usage

go get github.com/thlib/go-timezone-local/tzlocal

Included example

A runnable example is available in example/main.go. It prints the operating system, detected IANA time zone, and current local time.

The example imports time/tzdata, so the IANA time zone database is embedded in the executable. This is useful for standalone Windows builds where a time zone database may not otherwise be available.

Run it from the repository root:

go run ./example

Build and run it on Linux:

go build -o bin/timezone-example-linux ./example
./bin/timezone-example-linux

Cross-compile it for 64-bit Windows:

GOOS=windows GOARCH=amd64 go build -o bin/timezone-example-windows-amd64.exe ./example

Then run it from PowerShell on Windows:

.\bin\timezone-example-windows-amd64.exe

The generated bin/ directory is ignored by Git.

Use in your own program

Open your project folder
Create a file main.go

package main

import (
    "fmt"
    "time"

    "github.com/thlib/go-timezone-local/tzlocal"
)

func main() {
    tzname, err := tzlocal.RuntimeTZ()
    fmt.Println(tzname, err)

    // example:
    // tzname = "Europe/Berlin"

    // now you can use tzname to properly set up a location:
    loc, _ := time.LoadLocation(tzname)

    d0 := time.Date(2021, 10, 30, 20, 0, 0, 0, loc) // DST active:
    fmt.Println(d0)
    // 2021-10-30 20:00:00 +0200 CEST

    d1 := d0.AddDate(0, 0, 1) // add one day, now DST is inactive:
    fmt.Println(d1)
    // 2021-10-31 20:00:00 +0100 CET
}

Run the following commands:

go mod init example.com/yourpackage
go mod vendor
go run main.go

It should print the go runtime timezone.

For contributors to update the Windows time zone mapping

The generator downloads the latest IANA legacy names and Unicode CLDR Windows zone mappings, then rewrites tzlocal/tzmapping.go. It therefore requires network access to data.iana.org and raw.githubusercontent.com.

From the repository root, run:

go generate

If it reports GOPROXY list is not the empty string, but contains no entries, the configured GOPROXY is malformed. To override it for this command in a POSIX shell or WSL, run:

GOPROXY=https://proxy.golang.org,direct go generate

Credits

All credit goes to the various contributors, colm.anseo and MrFuppes for providing the following answers:

• https://stackoverflow.com/a/68938947/175071
• https://stackoverflow.com/a/68966317/175071

License

This project is dual‑licensed:

• The Unlicense (public domain). See LICENSE.
• Apache License 2.0. See LICENSE-APACHE.txt.

You may choose either license at your option.

Third‑party licences

This repository depends on several third‑party Go packages, for example golang.org/x/sys that are distributed under the BSD 3‑Clause licence.