[javascript] How to convert Moment.js date to users local timezone?

I use the Moment.js and Moment-Timezone frameworks, and have a Moment.js date object which is explicitly in UTC timezone. How can I convert that to the current timezone of the browser?

var testDateUtc = moment.tz("2015-01-30 10:00:00", "UTC"); var localDate = ???

So it would be fine if I could find out the users local time zone; or alternatively I'd like to convert the date object into another data object which just uses the "local timezone", no matter what that actually is.

Here's what I did:

var timestamp = moment.unix({{ time }});
var utcOffset = moment().utcOffset();
var local_time = timestamp.add(utcOffset, "minutes");
var dateString = local_time.fromNow();

Where {{ time }} is the utc timestamp.

You do not need to use moment-timezone for this. The main moment.js library has full functionality for working with UTC and the local time zone.

var testDateUtc = moment.utc("2015-01-30 10:00:00");
var localDate = moment(testDateUtc).local();

From there you can use any of the functions you might expect:

var s = localDate.format("YYYY-MM-DD HH:mm:ss");
var d = localDate.toDate();
// etc...

Note that by passing testDateUtc, which is a moment object, back into the moment() constructor, it creates a clone. Otherwise, when you called .local(), it would also change the testDateUtc value, instead of just the localDate value. Moments are mutable.

Also note that if your original input contains a time zone offset such as +00:00 or Z, then you can just parse it directly with moment. You don't need to use .utc or .local. For example:

var localDate = moment("2015-01-30T10:00:00Z");

Use utcOffset function.

var testDateUtc = moment.utc("2015-01-30 10:00:00");
var localDate = moment(testDateUtc).utcOffset(10 * 60); //set timezone offset in minutes
console.log(localDate.format()); //2015-01-30T20:00:00+10:00

var dateFormat = 'YYYY-DD-MM HH:mm:ss';
var testDateUtc = moment.utc('2015-01-30 10:00:00');
var localDate = testDateUtc.local();
console.log(localDate.format(dateFormat)); // 2015-30-01 02:00:00

1. Define your date format.
2. Create a moment object and set the UTC flag to true on the object.
3. Create a localized moment object converted from the original moment object.
4. Return a formatted string from the localized moment object.

See: http://momentjs.com/docs/#/manipulating/local/