JavaScript check if timezone name valid or not

Question

Is there a way to check if timezone name valid or not in JavaScript without using external library?

When user enters timezone name in text field I want to verify whether zone is valid or not?

I know we can do it easily using moment-timezone library. But I don't want to use any extra library. I'm looking for pure JavaScript way.

isValidTimeZone(name) {
//return true/false  
}

isValidTimeZone('Asia/Colombo'); //returns true
isValidTimeZone('America/Los_Angeles'); //returns true
isValidTimeZone('MyTimeZone/ME'); //returns false

Time zones are not considered valid based on the friendly location name (as you show in your question), they are valid based on a time zone offset. https://stackoverflow.com/questions/22609927/regular-expression-timezone — Scott Marcus, May 22 '17 at 14:39
User enters timezone name (ex: Asia/Colombo). Later I need to use this in Highcharts. So need to validate this. User will not enter +05:30. — Pratap A.K, May 22 '17 at 14:41
What makes a time zone valid for you? Is `America/Anaheim` valid? Because I don't think you mean that anything in "Continent/City_Name" format is automatically valid. You must have some database to test against. — Álvaro González, May 22 '17 at 15:00
Do you feel like maintaining [this data](https://github.com/moment/moment-timezone/blob/develop/data/packed/latest.json) yourself? Seems like a lot of trouble to go to in order to avoid using a library. — Joe Clay, May 22 '17 at 15:00
If you don't want use an external lib then there's no magic but write a map yourself. Checkout https://github.com/dmfilipenko/timezones.json or moment-timezone for a reference. — rstar, May 22 '17 at 15:07
They aren't just "friendly" names, they are identifiers in the tz database. The list is here: https://en.wikipedia.org/wiki/List_of_tz_database_time_zones — Matt Johnson-Pint, May 22 '17 at 17:00

score 64 · Accepted Answer · edited Jun 24 '21 at 01:25

In environments that fully support IANA time zone identifiers in ECMA-402 (ECMAScript Internationalization API), you can try using a time zone in a DateTimeFormat (or in the options of to toLocaleString) and it will throw an exception if it is not a valid time zone. You can use this to test for validity, but only in environments where it is supported.

function isValidTimeZone(tz) {
    if (!Intl || !Intl.DateTimeFormat().resolvedOptions().timeZone) {
        throw new Error('Time zones are not available in this environment');
    }

    try {
        Intl.DateTimeFormat(undefined, {timeZone: tz});
        return true;
    }
    catch (ex) {
        return false;
    }
}

// Usage:
isValidTimeZone('America/Los_Angeles') // true
isValidTimeZone('Foo/Bar') // false

If you cannot be assured of your environment, then the best way would be with moment-timezone

!!moment.tz.zone('America/Los_Angeles') // true
!!moment.tz.zone('Foo/Bar') // false

Of course, you could always extract your own array of time zone names (perhaps with moment.tz.names() and test against that.

score 14 · Answer 2 · answered Apr 29 '20 at 23:06

14

in typescript you could also do in a more cleaner way

    public static isValidTimezone(timezone: string): boolean {
            return moment.tz.zone(timezone) != null;
        }

you need to also import

import moment = require("moment-timezone");

answered Apr 29 '20 at 23:06

Pravin Bansal

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score 5 · Answer 3 · answered Jun 23 '22 at 10:57

I took Matt Johnson-Pin solution, after writing unit tests I found if to pass undefined the function returns true. So I made small update:

export const isValidTimeZone = (tz: unknown): boolean => {
    try {
        if (!Intl || !Intl.DateTimeFormat().resolvedOptions().timeZone) {
            return false
        }

        if (typeof tz !== 'string') {
            return false
        }

        // throws an error if timezone is not valid
        Intl.DateTimeFormat(undefined, { timeZone: tz })
        return true
    } catch (error) {
        return false
    }
}

Thanks anyway I use this in production.

JavaScript check if timezone name valid or not

3 Answers3

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