Get Epoch time value for different TimeZone - javascript

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);

Related

How to format a string in UTC to the configured timezone on Moment

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.

Angular 6 Typescript new Date is created in UTC, but I need in my local timezone

In my file HomeComponent.ts (not in template html). I create a new Date and show it in console like this:
var fecha = new Date();
console.log(fecha);
the time in my country now is 16:09 (UTC -3) but the console output shows the date in UTC:
Date 2018-12-20T19:09:32.910Z // the time is 19:09
I need to compare and do some operations with "this new date" and other dates saved in a DB so I need the new Date to be created in my local timezone. How can I create a new Date in my local timezone?
How can I create a new Date in my local timezone?
Dates don't have a timezone, they are simply an offset from 1970-01-01T00:00:00Z (a time value) so are effectively always UTC. They represent a particular moment in time and can be used to generate a string representing an equivalent date and time in any timezone.
The local offset comes from the host system, it's used (if necessary) when creating a date and when working with local date and time values. There are equivalent UTC methods for doing operations that don't consider the local timezone.
The default toString method will generate a timestamp for the host timezone, toISOString will use UTC, toLocaleString can be used to generate a timestamp for any timezone. All will represent the same UTC date and time, just in different timezones.
When comparing dates, it's the UTC time value that is compared as it provides a common factor for all dates.
the time in my country now is 16:09 (utc -3) but the console output show the date in utc
A Date or DateTime is a structure, it does not have a format. If you want to display a formatted date string using the timezone of the browser then call toLocaleString.
var fecha = new Date();
console.log("As ISO8601 in utc:", fecha);
console.log("As local:", fecha.toLocaleString());

In javascript, how to get timezone value in UTC format for new Date(2017,05,31).toISOString()?

How to get timezone value for new Date(2017,05,31).toISOString()? It always comes as 000Z for any Date when the date is passed to the Date constructor. But for new Date().toISOString(), it gives the the timezone value.
new Date(2017,05,31).toISOString() gives "2017-05-30T18:30:00.000Z"
and new Date().toISOString() gives "2017-06-07T15:29:23.692Z". How to get timezone in UTC format for the past dates?
If you want the time to default to midnight in UTC, you can use Date.UTC(year, month, ...) to first create a timestamp based in UTC.
var utcMay31 = Date.UTC(2017, 4, 31); // note: 4 = May (0 = January)
Then, create the Date from that timestamp.
new Date(utcMay31).toUTCString(); // "Wed, 31 May 2017 00:00:00 GMT"
However, if you're wanting to know the timezone stored in the Date object, it doesn't actually have that. Dates represent an "instant" in time as the total number of milliseconds that have passed since Jan 1, 1970 00:00:00.000 UTC.
new Date().getTime(); // 1496851...
A Date can tell you the user's local offset from UTC in minutes at that instant.
new Date().getTimezoneOffset(); // e.g. 0, -480, 300
Otherwise, the timezone is limited to two choices when creating date strings, and the choice is based on the method used – user's local timezone or UTC.
new Date().toString(); // "now" in user's local time
new Date().toUTCString(); // "now" in UTC time
new Date().toISOString(); // "now" also in UTC time, alternate format
// etc.
You're confused ISO date values do not show the "time zone" instead they show the UTC time. Z stand for Zulu (UTC time).
2017-06-07T15:29:23.692Z
The bold part is not the time zone. It is the milli-seconds, the full time is in UTC. The reason it shows a 000Z in the set Date is because you didnt' set the milli-seconds.
If you want to display the time zone use toUTCString(). However it will display GMT which is UTC/Greenwich Time. To display the local time zone in a the date format you can use date.toLocaleString('en-US',{timeZoneName:'short'}) for example will display the date plus the local US time zone. Or you can use toString() which will display the GMT offset + the long local time zone.
In javascript, parsing, rendering and constructing dates will always assume local. It will convert to a timestamp, the number of milliseconds since 1-1-1970 00:00:00. JSON.stringify will convert to a UTC string, but legacy framworks use local dates. Always beware of this.
var myDate = new Date(); // this is now.
you can get your timezoneoffset (in minutes) with myDate.getTimezoneOffset(), but this will return the same offset for every date (aside from daylight saving time)
You shouldn't do this:
var utcDate = new Date(+d+60000*d.getTimezoneOffset());
// +d convert the date to a timespan.
// getTimezoneOffset() is in minutes
// *60000 makes that in milliseconds, the scale timespans operate upon
Date has a few methods to format dates, but always as local or UTC date. You need to do it manually if you want different time zones.
Note: the Date.UTC(...) function returns a timestamp. You sometimes see shifted dates, so they behave like UTC. But this causes problems later on.
var date = new Date(2000,1,1,12,0,0);
// DO NOT USE (breaks at start of daylight saving time)
// these are date/times that have the UTC-value,
// but Javascript treats them like local dates with this value.
utcDate1 = (+date-60000*d.getTimeZoneOffset()); // minus!!
utcDate2 = new Date(Date.UTC(2000,1,1,12,0,0));
// DO NOT USE (breaks at start of daylight saving time)
BTW
Edge, Chrome and Firefox display dates differently in the console: Edge and Firefox always shows local date, Chrome shows UTC. Also, if you change your timezone, Edge will screw up.

moment-timezones.js, how to convert date in spesific timezone to utc, disregarding my local timezone?

my system uses timezone UTC+03:00 ,
im trying to get a date in string format, represented by NY timezone,
and convert it to a Date object in utc
const dateInNY = moment.tz(xlsxDate, "M/D/YYYY h:mm a", "America/New_York")
.tz("Z").toDate();
doesnt work correctly
how am i even suppose to convert to utc time?
-----------edit---------------
i got it to work, using the timezone "Africa/Accra" , where UTC offset is 0, and ther is no daylight savings time:
moment.tz(xlsxDate, "M/D/YYYY h:mm a", "America/New_York").tz("Africa/Accra")
but this solution is a bad workaround, and if the government of Accra decide to change the time laws, will stop working!
is there a way to set the utc offset to 0 in momentjs-timezones?
As Álvaro González mentioned, that Date object does not contain Time zone information.
I do the following:
new Date(moment.tz(date, currentTimezone).tz(newTimezone).format('YYYY/MM/DD HH:mm:ss'))
where date is a date object or a string (e.g. '2017-10-30 16:30:00.0000')
so, I change date from currentTimezone to newTimezone and after that new Date object will be returned
Let's change '2017-10-30 16:30:00.0000' from UTC to America/Toronto (UTC-4)
new Date(moment.tz(date, 'UTC').tz('America/Toronto').format('YYYY/MM/DD HH:mm:ss'))
And I got
Mon Oct 30 2017 12:30:00 GMT+0400
GMT+0400 is my timezone and console.log() just shows it with any
date object and it can mislead you. Please, don't look at the this
timezone.
Let's change '2017-10-30 16:30:00.0000' from Europe/Samara (UTC+4) to America/Toronto (UTC-4)
new Date(moment.tz('2017-10-30 16:30:00.0000', 'Europe/Samara').tz('America/Toronto').format('YYYY/MM/DD HH:mm:ss'))
Firstly, moment.tz undertands that date has no timezone information and associate with Europe/Samara (UTC+4)
timezone. After that computes difference between new and old
timezone (it's -8 hours in this case)
And returns result
Mon Oct 30 2017 08:30:00 GMT+0400
And answer on your question
If xsltDate is a date object or string which do not contain timezone information
dateUTC = new Date(moment.tz(xlsxDate, "America/New_York").tz("UTC").format('YYYY/MM/DD HH:mm:ss'));
If xsltDate contain timezone information (e.g.'2013-06-01T00:00:00-04:00'), then no need to tell moment.tz which timezone xlsxDate has, just mention a new timezone
dateUTC = new Date(moment.tz(xlsxDate, "UTC").format('YYYY/MM/DD HH:mm:ss'));
Short answer is that you cannot.
The .toDate() method of the Moment library returns a native Date object. Such objects do not keep memory of any specific time zone (that's one of the reasons to use Moment in the first place), they just keep track of the exact time moment represented and merely pick a time zone when formatting to string, which is either UTC or the browser's time zone (not an arbitrary one).
The long answer is that you're probably getting correct results but are printing them with a method that uses the browser's time zone.
i found a function that does what i was trying to do, it belongs to the momentjs library itself: utcOffset(n) sets the offset to n.
(i also had to explicitly write the date string format correctly, thanks VincenzoC)
this is the code i was trying to write:
const dateInNY = moment.tz(xlsxDate, "M/D/YYYY h:mm a", "America/New_York");
const dateUTC = dateInNY.utcOffset(0).toDate();
however, the toDate function changes the timezone to my local timezone anyway, so .utcOffset(0) is redundat, and i can just use moment this way:
const dateInNY = moment.tz(xlsxDate, "M/D/YYYY h:mm a", "America/New_York");
const dateUTC = dateInNY.toDate();
and change the Date objects date to utc time later (in my case, the JSON.stringify stuff i use later does that for me)

moment.js does not convert timestamps with specific timezones to unix timestamps

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

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