I am a bit confused with this, i know the code gives me the time difference from GMT, but for which city or country? How do i get the time difference between gmt and the time in Kabul Afghanistan.
var now = new Date();
alert(now.getTimezoneOffset());
The difference is the value showing in the alert.
It gives you the offset of the client local time zone.
To get the offset of different time zone, use external libraries as stated here, or just get the offset manually and use it, as explained here.
Related
At the time of this post my current time is 2017-01-10T19:23:00.000Z
but new Date() gives me 2017-01-11T00:23:19.521Z 5 hours ahead of my current timezone. This affects the way my data is stored in my MongoDB. I know I can set the time to 5 hours ago using
var datetime = new Date();
datetime.setHours(datetime.getHours()-5);
But I will prefer a better way to do this. I tried using this. I still got the same time. In other parts of my code I get Tue Jan 10 2017 19:54:30 GMT-0500 (EST) different from the initial time. I will be happy if someone can point out what's wrong here.
Using moment.js is the easiest way to accomplish what you are asking.
moment().format() // "2017-01-11T13:56:15-05:00"
The output is a string in ISO-8601 format, with time zone offset in effect in your local time zone.
You could do this yourself with a lot of code that reads the various properties of the Date object, building a string from those values. But it is not built-in to the Date object in this way.
Also, note any time you try to adjust a Date object by a time zone offset, you are simply picking a different point in time. You're not actually changing the behavior of the time zone being used by the Date object.
If you don't want to use any exteral JS file, You can simply use following code to get current timezone.
new Date().toString();
I'm using momentjs lib to updated text on some ajax action. What I need to do is to set a current date & time in london. I'm using moment.utc() function but because of the summer time I'm one hour out.
For example running this on 14:26
console.log( moment.utc().format('HH:mm:ss') );
I'm getting 13:26:53.
Any idea on how to fix this?
Can you use momentJS timezone?
moment().tz('Europe/London');
EDIT: In case you try to use this without seeing the link, it's a separate library you have to include.
If you want the local time instead of the UTC time, just use moment() instead of moment.utc(). You're specifically asking for UTC, so you shouldn't be surprised when you get UTC :)
From the documentation:
By default, moment parses and displays in local time.
If you want to parse or display a moment in UTC, you can use moment.utc() instead of moment().
This brings us to an interesting feature of Moment.js. UTC mode.
While in UTC mode, all display methods will display in UTC time instead of local time.
This is assuming you always want the user's local time. If you want a specific time zone (London) which may not be the user's time zone and isn't UTC, then you should use the library indicated by Takuya's answer. I would think carefully before doing so though - while it may be a sensible approach, you should at least validate that first. It's often reasonable to display a time for user U1 in the time zone of user U2 - but here you're using a fixed time zone. That's only appropriate if you know that U2 will always be in London. It would be really confusing if actually U2 is in some other zone - either the same as or different to U1.
I need to get a timezone from a time, date is not important, but daylight savings is.
something like:
timezone = function("15:00");
Is there a simple way to do this?
I dont think you can get the timezone from the time but you might get some help from Date.prototype.getTimezoneOffset()
The getTimezoneOffset() method returns the time-zone offset from UTC,
in minutes, for the current locale.
Example:
var x = new Date();
var currentTimeZoneOffsetInHours = x.getTimezoneOffset() / 60;
No, of course not. Think about it, you're passing 15:00 to that function, presumable denoting it's 3PM. But in what timezone is it 3 PM? No way of knowing. It's like me saying it's quarter to, without saying what hour it's quarter to to.
The only way you can get a timezone in JS is by using the Date object, but that just shows the timezone of the machine on which your code is running, nothing about the TZ that "created" the time you're processing.
Also note that daylight saving isn't a global phenomenon, quite the contrary. AFAIKT, there isn't a single time-zone where DST has always been in place...
In order to get TimeZone information you need more than a Date (and an offset). You need a location.
Javascript does not know the location that it resides in but it does know the current offset from UTC. That is different than a Time Zone. The daylight savings time issue play havoc with this key difference.
This has posed problems when dealing with server applications that know their timezone and report dates as being in a specific Time Zone.
My rule of thumb has been fairly simple in this regard.
Always use Long or long (a 64 bit number) to store, pass and process dates times or intervals, only convert to Date, Calendar or DateTime objects when interacting with people.
Once you have a date object, such as with new Date(), you can use .getTimezoneOffset() to get the number of minutes between the date's object and UTC, which is timezone information you can use.
First off, I am NOT looking for whether DST is in effect locally.
I'm running a Node process that has data that has associated timestamps. I need to convert those timestamps to a day/month/year in a specified time zone, but all I'm given is the time zone's offset and DST offset.
I wish Date / Moment worked better with time zones. They work great with UTC or Local time zones, but it seems you need to hack it to get something else.
Is there something I'm missing? Assuming I can determine whether DST is in effect, would this work:
var d = new Date(ts + timezone_offset - local_offset);
d.getMonth();
d.getDate();
where timezone_offset is the time zone's offset (either the standard offset or the dst one)?
How might I determine whether DST is in effect?
First, recognize that if all you have are the offsets, you cannot solve this problem. You must have a time zone identifier, such as "America/New_York". Since in the question comments you said you do indeed have this, then you can use one of these libraries to get the job done.
I had previously posted another answer to this question, recommending TimeZoneJS, but I'll retract that now - as this question is specifically about DST, and TimeZoneJS has bugs, reporting values incorrectly near DST transitions.
Instead, I'll now recommend using moment.js with the moment-timezone add-on. Once installing both libraries (being sure to load actual time zone data, per the docs), the code is quite simple:
moment(timestamp).tz(timezone).isDST()
For example:
moment(1451624400000).tz('America/New_York').isDST(); // false
moment(1467345600000).tz('America/New_York').isDST(); // true
Or, if your timestamps are already strings in terms of the local time, then use this syntax instead:
moment.tz('2016-01-01T00:00:00','America/New_York').isDST(); // false
moment.tz('2016-07-01T00:00:00','America/New_York').isDST(); // true
Is there something I'm missing? Assuming I can determine whether DST is in effect, would this work where timezone_offset is the requested time zone's offset?
Try to always use the UTC methods to get attributes of dates. That way your (server's) local timezone will not affect any calculations:
var d = new Date(ts + timezone_offset);
d.getUTCMonth();
d.getUTCDate();
How might I determine whether DST is in effect?
That's complicated. There are/were many different algorithms to determine DST beginning and end, depending on the region - have a look at http://en.wikipedia.org/wiki/Daylight_saving_time_by_country for example.
I don't know whether there are any libraries that have already coded these, or maybe even contact the timezone database for correct information. The last resort would be to ask the user himself for timezone details.
moment.js (http://momentjs.com/) has a isDST function. You could use moment (lots simpler), or check how it is implemented.
moment(your_date).isDST();
I want to get the time on the computer of the person who is accessing my website. Should I use getHours() or getUTCHours()?
Short answer is it depends. If you want the hours as it displays on a clock for their timezone you will want getHours() as it returns the hours in their local time. If you want the hours in Universal Time (no timezone adjustment) then use getUTCHours()
I would recommend getUTCHours - keeping everything in UTC removes a lot of headaches when it comes to working with dates and times.
getHours will return the time according to their timezone, getUTCHours will get their time converted to UTC. Would probably be easier to use getUTCHours so everyone is returning their time in the same timezone.
It depends what you're using it for. If you want to get the user's local time, use getHours(). If you want to get something like a time offset (say, "hours until the new CoD is released in the UK"), use getUTCHours() as an absolute reference point. Bear in mind, however, that if the user's clock is set wrong, getUTC*() functions will return times that aren't really UTC - all they do really is remove the getGMTOffset() amount for you.
It depends on what you want to do, but i'd agree with Andrew, if you use getUTC*** it becomes easier for you to handle dates and times