In an JS app, I receive timestamp (eq. 1270544790922
) from server (Ajax).
Basing on that timestamp I create Date
object using:
var _date = new Date();
_date.setTime(1270544790922);
Now, _date
decoded timestamp in current user locale time zone. I don't want that.
I would like _date
to convert this timestamp to current time in city of Helsinki in Europe (disregarding current time zone of the user).
How can I do that?
A Date object's underlying value is actually in UTC. To prove this, notice that if you type new Date(0)
you'll see something like: Wed Dec 31 1969 16:00:00 GMT-0800 (PST)
. 0 is treated as 0 in GMT, but .toString()
method shows the local time.
Big note, UTC stands for Universal time code. The current time right now in 2 different places is the same UTC, but the output can be formatted differently.
What we need here is some formatting
var _date = new Date(1270544790922);
// outputs > "Tue Apr 06 2010 02:06:30 GMT-0700 (PDT)", for me
_date.toLocaleString('fi-FI', { timeZone: 'Europe/Helsinki' });
// outputs > "6.4.2010 klo 12.06.30"
_date.toLocaleString('en-US', { timeZone: 'Europe/Helsinki' });
// outputs > "4/6/2010, 12:06:30 PM"
This works but.... you can't really use any of the other date methods for your purposes since they describe the user's timezone. What you want is a date object that's related to the Helsinki timezone. Your options at this point are to use some 3rd party library (I recommend this), or hack-up the date object so you can use most of it's methods.
Option 1 - a 3rd party like moment-timezone
moment(1270544790922).tz('Europe/Helsinki').format('YYYY-MM-DD HH:mm:ss')
// outputs > 2010-04-06 12:06:30
moment(1270544790922).tz('Europe/Helsinki').hour()
// outputs > 12
This looks a lot more elegant than what we're about to do next.
Option 2 - Hack up the date object
var currentHelsinkiHoursOffset = 2; // sometimes it is 3
var date = new Date(1270544790922);
var helsenkiOffset = currentHelsinkiHoursOffset*60*60000;
var userOffset = _date.getTimezoneOffset()*60000; // [min*60000 = ms]
var helsenkiTime = new Date(date.getTime()+ helsenkiOffset + userOffset);
// Outputs > Tue Apr 06 2010 12:06:30 GMT-0700 (PDT)
It still thinks it's GMT-0700 (PDT), but if you don't stare too hard you may be able to mistake that for a date object that's useful for your purposes.
I conveniently skipped a part. You need to be able to define currentHelsinkiOffset
. If you can use date.getTimezoneOffset()
on the server side, or just use some if statements to describe when the time zone changes will occur, that should solve your problem.
Conclusion - I think especially for this purpose you should use a date library like moment-timezone.