Getting moment.js to show datetimes appropriate to info being viewed

Question

Previous answers on here pointed me to moment.js for javascript date handling and I am really happy to find it. I can parse and manipulate quite happily.

The users on my website look at info relating to diverse physical sites/locations, and I want to show associated datetimes in the time specific to that location, not the users location.

Each physical site has a timezone attribute string like "Europe/London" or "Europe/Amsterdam"

My datetimes are all stored and delivered from the DB in UTC.

Is there a clever simple way I can render my moment.js object in any specified timezone?

Answer 1

Theoretically, you could do something like this.

moment.fn.formatInZone = function(format, offset) {
    return this.clone().utc().add('hours', offset).format(format);
}

moment().formatInZone('HH:mm:ss', 7);
moment().formatInZone('HH:mm:ss', -7);

However, this requires that you know the correct offset, so it won't take into consideration daylight saving time.

Answer 2

If you want to display dates in ANOTHER timezone than the user is actually in, then you need to start looking into stuff like https://bitbucket.org/pellepim/jstimezonedetect (if you need to detect which timezone a user is in) and https://github.com/mde/timezone-js if you need to localize dates between zones.

jsTimezoneDetect which I linked to above will help you provide a shortlist of relevant timezones.

That you have your datetimes stored in UTC will make it pretty damn easy for you thanks to mde/timezone-js.