Moment.Js: Offsetting dates using UTC and Timezone offset

Question

I am trying to adjust a time using a timezone offset and a UTC timestamp.

I am running the following code:

var date = {
    utc: '2013-10-16T21:31:51',
    offset: -480
}

var returnDate = moment(date.utc).utc().zone(date.offset).format('MM/DD/YYYY h:mm A');

What I am expecting is: 10/16/2013 1:31 PM but I am ending up with 10/17/2013 9:31 AM

Solution 1

Here is what worked for me:

var date = {
  utc: '2013-10-16T21:31:51',
  offset: 480
}

var returnDate = moment.utc(date.utc).zone(date.offset).format('MM/DD/YYYY h:mm A');

If you noticed, I changed the offset to a positive number. This gave the desired result. If the offset was left at -480 the output was 10/17/2013 5:31 AM.

There is a moment#UTC method that initializes the date as UTC vs. local time.

Solution 2

I use the jsTimezoneDetect library to determine the timezone name instead of the offset.

Then use this on a UTC timestamp:

timestamp = moment.tz(timestamp, tz.name());
timestamp.format('MM/DD/YYYY h:mm A');

Comments

[Neil Kistner]

What does the date look like if you remove the .utc().zone(date.offset)? So that way you call just .format() on it.

[Neil Kistner]

Also, if looking at the documentation here and scroll down a little bit. It reads, "Unless you specify a timezone offset, parsing a string will create a date in the current timezone."

[Neil]

I've posted bad data, let me correct this. sec

[Neil]

It looks like this: 10/16/2013 9:31 PM with moment(date.utc).format('MM/DD/YYYY h:mm A');

[Neil Kistner]

What is the current timezone of the server this is running on? If it is not in UTC, you are passing in a UTC date already, and then calling .utc() on it, which is further advancing the time.

[Neil]

I'm unsure of the server time, these dates are coming from a database of events, when they occur. When I use moment(date.utc).zone(date.zone).format('MM/DD/YYYY h:mm A'); I end up with 10/17/2013 9:31 AM again

[Jason Sperske]

I think if you are going to be adjusting for timezone then you will have to become sure of the server timezone because moment.js is parsing the date from the users browser.

[potench]

For other's stumbling on this post, you can use a string for the offset that's perhaps more legible: zone('-07:00') (PST example)

[godimedia]

moment.zone() is deprecated after moment 2.9.0

[medBouzid]

the method zone() is deprecated, everyone should use utcOffset() instead see here github.com/moment/moment/issues/1779