I am using moment.js to convert a bunch of timestamps in it's specific timezone to a unix timestamp like this:
var timestamp = "2015-12-29T09:35:00.000-08:00";
console.log(moment("2015-12-29T09:35:00.000-08:00").unix();
console.log(moment("2015-12-29T09:35:00.000-08:00").tz("America/Los_Angeles").unix();
The console log of both the above statements is for some reason, the same - 1451361900. This unix timestamp which it is logging is in my local timezone and not the one I asked for: "America/Los_Angeles". What am I missing?
A unix timestamp, or Posix, should always be in the UTC (Coordinated Universal Time) format.
Moment is just doing something like
function unix () {
return Math.floor(+this / 1000);
}
Where it converts the date object to an integer and then converts from milliseconds to seconds.
The starting point is a regular javascript Date object, and the ECMA standard says
Date objects are based on a time value that is the number of
milliseconds since 1 January, 1970 UTC.
so date objects are always UTC when converted to the number of milliseconds since 1. January 1970 (epoch), i.e. you can't set another timezone on a Unix timestamp, both your dates are the same.
The proper way is to use moment-Timezone is this.
console.log(moment("2015-12-29T09:35:00").unix());
console.log(moment.tz("2015-12-29T09:35" , "America/Los_Angeles").unix());
In above your are providing time zone as a string too which is this last part ".000-08:00" and then you are providing another zone, which is incorrect.
As you are trying to find out the unix timestamp for the date "2015-12-29T09:35:00.000-08:00". In this date format timezone value is already present which is "-08:00", hence you get the same unix timestamp.
For getting the unix timestamp desired solution, remove the timezone value and use moment-timezone as :
console.log(moment.tz("2013-12-01", "America/Los_Angeles").unix());
For more details check moment-timezone
Related
I have the following string, which is in UTC:
2022-02-01T00:00:00Z
I have already configured my timezone, so I do not want to mess/call .tz()
I know that this string is in UTC, but I am not managing to convert from UTC to the defined timezone, which in this example is pacific/wallis.
I have tried many things, as
const utc = moment.utc('2022-02-01T00:00:00Z').toDate()
const inConfiguredTimeZone = utc.format()
My desire is to get this timestamp 2022-02-01T00:00:00Z and have converted to the defined timezone on Moment
I need to tell moment that "This string is in UTC, please give me the converted timestamp in the defined time zone"
If you just want to format a UTC timestamp in your current timezone (determined by your computer's time settings) just use
let s = moment("2022-02-01T00:00:00Z").format();
This will produce a string like 2022-02-01T12:00:00+12:00 if you are currently in a timezone that has a UTC offset of +12 hours (like pacific/wallis) or 2022-02-01T01:00:00+01:00 if you are currently in a timezone that has a UTC offset of +1 hours (like europe/berlin)
If you want it converted to a specific timezone use
let s = moment("2022-02-01T00:00:00Z").tz("pacific/wallis").format();
This will produce 2022-02-01T12:00:00+12:00, regardless of your current timezone.
My local time zone is IST , i tried to define timezone inside Date object like
const usaRegionTime = new Date(inputDate.toString()).toLocaleString(
'en-US',
{
timeZone: 'America/New_York',
}
);
const estDate = new Date(usaRegionTime);
console.log(estDate.getTime());// Uses IST(local time Zone) instead of EST(Specifed time zone)
Example:
My IST time is 7:15 PM and i use the Date object with EST timeZone i get correct EST as 9:45 AM but when i try est.getTime() UTC is calculated as 7:15 pm instead of 1:45 pm . Its taking 9:45 am as IST(Local time Zone) before converting to UTC(Epoch).
Problem is its Taking Browser local timeZone(IST) instead of TimeZone(EST) i gave as param to Date object to get Epoch value . Is there a way to override the Local time Zone with Specified TimeZone while getting Epoch value.
Is there a way to override the Local time Zone with Specified TimeZone while getting Epoch value.
No. You can generate a timestamp for any supported IANA representative location, but you can't "set a timezone" for the Date instance itself.
ECMAScript Date objects are just a time value that is an offset in milliseconds from 1 Jan 1970 UTC. They have no timezone and can only work in either the local timezone or UTC, that's it. When parsing a timestamp for a particular timezone, the result is a UTC time value. That is the only thing the Date instance remembers so it doesn't matter how you generate a Date, the time value is always effectively UTC.
The plain get and set methods like getYear, getMintues, etc. and the toString methods use the UTC time value and host settings to generate local date and time values. The UTC get and set methods like getUTCYear, getUTCMintues, etc. and toISOString, toUTCString etc. return UTC values. So you can work in either local or UTC, working in some other timezone or location requires you to do the work (which is quite complex and likely a library is a better option).
You can get a timestamp for any supported IANA representative location using toLocaleString with the timeZone option, however that only affects the generated string, it doesn't change the underlying UTC time value.
You can't set a timezone or location for a Date object as it doesn't have any property on which to set it, it's just a (UTC) time value, that's it.
Also, the built–in parser is not required to parse the output from toLocaleString, primarily because the user can configure the output to a huge number of different formats that may not include any date or time values (e.g. you can get just the timezone or offset). So depending on parsing such values is fundamentally flawed.
var date= new Date().valueOf(); //gives UTC timestamp in millisecond
const usaRegionTime = new Date(date).toLocaleString(
'en-US',
{
timeZone: 'America/New_York',
}
);
const estDate = new Date(usaRegionTime).toString();
console.log(estDate);
I wish to create a new Date in JS, but have it be cast as UTC time. For example, suppose castAsUTC() produces the following desired effect:
var x = new Date('2019-01-01T00:00:00') // In local time (PST)
castAsUTC(x).toISOString(); // => '2019-01-01T00:00:00Z'
// x.toISOString() gives us '2019-01-01T08:00:00Z', which is undesired
Currently, my function looks like this:
function castAsUTC(date) {
return new Date(x.toLocaleString() + '+00:00');
}
Is there a cleaner/nicer way of producing the same effect? Thanks in advance!
EDIT: To be more specific, I'm interested in transforming the date's timezone, without changing its actual value with as little arithmetic as possible. So calling .toISOString() will produce the same date as it is in local time.
I am currently using the moment-timezone library, but I can't seem to get the desired effect using that, either. I would definitely accept an answer that uses Moment.js
You can switch a Moment instance to UTC using the utc function. Then just use format to get whatever the specific output you want from it.
If indeed the string you have is like the one shown, then the easiest thing to do would be to append a Z to indicate UTC.
var input = '2019-01-01T00:00:00';
var date = new Date(input + 'Z');
var output = date.toISOString();
Or, if you would like to use Moment.js, then do this:
var input = '2019-01-01T00:00:00';
var m = moment.utc(input);
var output = m.format();
You do not need moment-timezone for this.
tl;dr;
You formatted the date wrong. Add the letter "Z" to the end of your date string and it will be treated as UTC.
var x = new Date('2019-01-01T00:00:00Z') // Jan 1, 2019 12 AM UTC
These formatting issues are easier to manage with a library like momentjs (utc and format functions) as described in other answers. If you want to use vanilla javascript, you'll need to subtract out the timezone offset before calling toISOString (see warnings in the longer answer below).
Details
Date in javascript deals with timezones in a somewhat counter intuitive way. Internally, the date is stored as the number of milliseconds since the Unix epoch (Jan 1, 1970). That's the number you get when you call getTime() and it's the number that's used for math and comparisons.
However - when you use the standard string formatting functions (toString, toTimeString, toDateString, etc) javascript automatically applies the timezone offset for the local computers timezone before formatting. In a browser, that means it will apply the offset for the end users computer, not the server. The toISOString and toUTCString functions will not apply the offset - they print the actual UTC value stored in the Date. This will probably still look "wrong" to you because it won't match the value you see in the console or when calling toString.
Here's where things really get interesting. You can create Date's in javascript by specifying the number of milliseconds since the Unix epoch using new Date(milliseconds) or by using a parser with either new Date(dateString). With the milliseconds method, there's no timezone to worry about - it's defined as UTC. The question is, with the parse method, how does javascript determine which timezone you intended? Before ES5 (released 2009) the answer was different depending on the browser! Post ES5, the answer depends on how you format the string! If you use a simplified version of ISO 8601 (with only the date, no time), javascript considers the date to be UTC. Otherwise, if you specify the time in ISO 8601 format, or you use a "human readable" format, it considers the date to be local timezone. Check out MDN for more.
Some examples. I've indicated for each if javascript treats it as a UTC or a local date. In UTC, the value would be Jan 1, 1970 at midnight. In local it depends on the timezone. For OP in pacfic time (UTC-8), the UTC value would be Jan 1, 1970 at 8 AM.
new Date(0) // UTC (milliseconds is always UTC)
new Date("1/1/1970"); // Local - (human readable string)
new Date("1970-1-1"); // Local (invalid ISO 8601 - missing leading zeros on the month and day)
new Date("1970-01-01"); // UTC (valid simplified ISO 8601)
new Date("1970-01-01T00:00"); // Local (valid ISO 8601 with time and no timezone)
new Date("1970-01-01T00:00Z"); // UTC (valid ISO 8601 with UTC specified)
You cannot change this behavior - but you can be pedantic about the formats you use to parse dates. In your case, the problem was you provided an ISO-8601 string with the time component but no timezone. Adding the letter "Z" to the end of your string, or removing the time would both work for you.
Or, always use a library like momentjs to avoid these complexities.
Vanilla JS Workaround
As discussed, the real issue here is knowing whether a date will be treated as local or UTC. You can't "cast" from local to UTC because all Date's are UTC already - it's just formatting. However, if you're sure a date was parsed as local and it should really be UTC, you can work around it by manually adjusting the timezone offset. This is referred to as "epoch shifting" (thanks #MattJohnson for the term!) and it's dangerous. You actually create a brand new Date that refers to a different point in time! If you use it in other parts of your code, you can end up with incorrect values!
Here's a sample epoch shift method (renamed from castAsUtc for clarity). First get the timezone offset from the object, then subtract it and create a new date with the new value. If you combine this with toISOString you'll get a date formatted as you wanted.
function epochShiftToUtc(date) {
var timezoneOffsetMinutes = date.getTimezoneOffset();
var timezoneOffsetMill = timezoneOffsetMinutes * 1000 * 60;
var buffer = new Date(date.getTime() - timezoneOffsetMill);
return buffer;
}
epochShiftToUtc(date).toUTCString();
If I run var myDate = new Date('29-06-2016 10:00'), myDate will only contain one thing: a number. The number of milliseconds from 01-01-1970 00:00:00 GMT to 29-06-2016 10:00:00 XXX
XXX being the timezone of the OS. In my case BST (because it is a summer date, in winter would be GMT).
Now... What if I want the milliseconds from 01-01-1970... to 29-06-2016 10:00:00 GMT-7?
I only found methods to tell me what time is in the GMT-7 timezone when in BST timezone is 29-06-2016 10:00:00, but that is not what I am looking for!
Also, to change an environmental variable so the timezone is GMT-7 is not an option.
I think you want the date string in the following format
"2016-06-29T10:00:00-07:00"
That lets you set the timezone relative GMT (not 100% sure on the timezone, but it's client side so does depend on their locale).
I had a similar thing where JS was changing the time on date objects and the only way I found was to set up the date and set this.
Bonus info, to get this from a .NET DateTime using the following string format.
"yyyy-MM-ddTHH:mm:sszzz"
I think I found a way of doing it, using moment.js as ErikS suggested:
// This code is running in a Node.js server configured to use UTC
// Incorrect date, as it is interpret as UTC.
// However, we do this to get the utcOffset
var auxDate = moment.tz(new Date('2016-6-23 10:15:0'), 'US/Mountain');
// Get the milliseconds since 1970 of the date as if it were interpreted
// as GMT-7 or GMT-6 (depends on the date because of Daylight Saving Time)
var milliseconds = auxDate.valueOf() - auxDate.utcOffset() * 60000;
My goal is to convert an integer expressing the Unix Epoch time (or the number of milliseconds since midnight of January 1, 1970) into a localized time for the UTC (or GMT) time-zone.
So I have this method:
function formatDateTimeFromTicks(nTicks)
{
//'nTicks' = number of milliseconds since midnight of January 1, 1970
//RETURN:
// = Formatted date/time
return new Date(nTicks).toLocaleString();
}
As an example I'm using the value of 1442004135000, which should give me 9/11/2015 8:42:15 PM for my locale (here's where you can check), but my method:
alert(formatDateTimeFromTicks(1442004135000));
gives me 9/11/2015 1:42:15 PM.
Any idea why and how to fix it?
The native Date object won't be enough, as even in the best case it doesn't give you a UTC and locale string. I strongly suggest you use the excellent moment library to have reliable behavior across all platforms.
To display nice localized UTC in French:
moment(1442004135000).utc().locale('fr').format('LLLL')
=> "vendredi 11 septembre 2015 20:42"