Parse dateTime string as UTC

Question

Timezones is constant pain in every datetime library I tried. So here's the question, suppose you have a UTC datetime provided as string: 2019-06-25T05:00:00Z. How do you create a UTC DateTime object out of it (I use luxon, but answer can be in terms of any library)?

console.info(luxon.DateTime.fromISO('2019-06-25T05:00:00Z').toSQL());

<script src="https://moment.github.io/luxon/global/luxon.min.js"></script>

When I run the snippet above I get:

2019-06-25 09:00:00.000 +04:00 // local timezone

While I need:

2019-06-25 05:00:00.000 -00:00 // UTC

Whaley

Looks like you have to tell it to use UTC as the zone for the instance. It parses the string correctly, it's just using your local timezone when building a new string. I've updated my answer to show how to do that. – Determinative

Answer 1

Three options for you:

1) Luxon's documentation says you could use fromISO to get a DateTime from it. That parses the string correctly. Looks like to get it formatted the way you want, you have to tell it to use the zone UTC, but that's because it's formatting on output:

const {DateTime} = luxon;
console.info(DateTime.fromISO('2019-06-25T05:00:00Z', { zone: "UTC"}).toSQL());

<script src="https://moment.github.io/luxon/global/luxon.min.js"></script>

You could also use setZone("UTC") on the result of fromISO.

2) JavaScript's built-in Date object will parse that as UTC (new Date(yourString)), since it's in the format defined in the spec. You can then use the UTC methods on it to get the UTC information (getUTCHours, etc.), or you can use the local date/time methods on it to get the local information (getHours, etc.). You can also use toISOString to get a UTC string:

console.info(new Date('2019-06-25T05:00:00Z').toISOString());

<script src="https://moment.github.io/luxon/global/luxon.min.js"></script>

3) Moment would also happily do so.

console.info(moment.utc('2019-06-25T05:00:00Z').toISOString());

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.26.0/moment.min.js"></script>

If you need +00:00 instead of Z, you can throw a replace at it, or with Luxon or Moment they offer full formatting options.

Determinative