UTC is of format - 1994-11-05T08:15:30-05:00
But why does Date.UTC gives a string representing milliseconds ?
How can I achieve the same in Javascript and what are the browser compatibility cases I need to take care of while doing without external library ( say moment ).
Date.UTC returns the date in the UTC/GMT timezone, as a Unix timestamp.
What you are referring to as UTC format is ISO-8601 format, and you retrieve that with the toISOString() method. For example:
var d = new Date();
var n = d.toISOString();
Related
I am using moment.js, and I want to convert from ISO Format date time to UTC time zone.
I can convert from local time to UTC+ISOformat, but I am not able to convert ISO format to UTC time zone.
Input:
2018-03-22T00:00:00Z
Expected output:
date should be in UTC time zone. If I calculate the it should be:
22018-03-21T18:30:00Z
First I want to convert into ISO, After that convert into UTC**.
Not able to Converted local date time to ISO then UTC
We can convert into string, But from ISO format can convert or not?
Fox example: I want to convert ISODATE(2018-03-22T00:00:00Z) into UTC time zone.
function toISO(dt) {
return moment(dt).format("YYYY-MM-DDTHH:mm:ss") + "Z";
}
var date = new Date();
var isoDate= toISO(date)
Direct we can convert
function toISOWithUtc(dt) {
return moment(dt).utc().format("YYYY-MM-DDTHH:mm:ss") + "Z";
}
var date = new Date();
toISO(date)
Both 2018-03-22T00:00:00Z and 2018-03-21T18:30:00Z already are in UTC.
Note the Z in the end? This means that the date is in UTC. It's not a hardcoded letter that you can just append to the end - it has a specific meaning, it tells that the date/time is in UTC.
If you want to convert that UTC date to another timezone (I'm guessing that's what you want), you can use moment.tz:
// convert UTC 2018-03-22T00:00:00Z to Asia/Kolkata timezone
moment.tz('2018-03-22T00:00:00Z','Asia/Kolkata')
Just change the timezone name to the one you want to convert.
And calling format() will give you the converted date/time in ISO8601 format:
moment.tz('2018-03-22T00:00:00Z','Asia/Kolkata').format() // 2018-03-22T05:30:00+05:30
Note that the offset changed from Z to +05:30. This means that the date/time above is 5 hours and 30 minutes ahead UTC, which is the result of converting 2018-03-22T00:00:00Z to Kolkata's timezone.
Note: I think you're mistaking the concepts here.
UTC is a time standard. It defines things like the current date/time accross the world, it uses atomic clocks to make sure everybody on Earth are synchronized, and timezones are all based on offsets from UTC.
ISO8601 is a standard for exchanging date/time-related data. It defines formats (text representations of dates). A date/time can be in ISO format, regardless of being in UTC or not.
That's why "convert from UTC to ISO" (or vice-versa) makes no sense at all.
Hello guys I was wondering how do I convert a date into Unix time stamp using the library moment.js so I can compare the oldDate with another date.
This is what I tried:
var oldDate = (moment.unix(1490632174)).format();
// here I got the Date in string format
var newDate= moment.utc('2017-03-27T18:29:59+02:00', "YYYY-MM-DD");
// now I want to convert it again into unix timestamp and I don't know how to do it.
console.log(oldDate, newDate);
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.18.1/moment.min.js"></script>
Documentation is a wonderful thing. Unix Timestamp (seconds)
moment().unix();
moment#unix outputs a Unix timestamp (the number of seconds since the Unix Epoch).
moment(1318874398806).unix(); // 1318874398
This value is floored to the nearest second, and does not include a milliseconds component.
var oldDate = moment.unix(1490632174).unix();
// here I got the Date in string format
var newDate= moment.utc('2017-03-27T18:29:59+02:00', "YYYY-MM-DD");
// now I want to convert it again into unix timestamp and I don't know how to do it.
console.log(oldDate, newDate.unix());
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.18.1/moment.min.js"></script>
You can use the < and > operators:
var oldDate = moment.unix(1490632174);
var newDate= moment.utc('2017-03-27T18:29:59+02:00', "YYYY-MM-DD");
console.log(oldDate<newDate, oldDate>newDate);
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.18.1/moment.min.js"></script>
Another way you could approach this is to leverage the native Date.parse("2017-03-27T18:29:59+02:00 GMT") method in Javascript. This method parses a date string and returns Unix Time in ms.
For more info, checkout Date.parse() documentation and this Unix Time Converter that makes use of both moment and the native JS method.
I have a date sting that looks like this 2016-02-21T02:14:39.000000
would like to convert it to Epoch time using Javascript if possible
Try
var ts = "2016-02-21T02:14:39.000000";
var unix_seconds = ((new Date(ts)).getTime()) /1000;
console.log(unix_seconds);
getTime returns milliseconds, so divide by 1000 to get seconds
https://jsfiddle.net/tbxac0de/
Presumably by "convert it to Epoch time" you mean a number of seconds or milliseconds since the common UNIX and ECMAScript epoch. The time value can be found by converting the string to a Date and getting its internal time value.
By far the best way to convert a string to a Date is to manually parse it. A library can help, but a function isn't difficult to write. E.g. to parse "2016-02-21T02:14:39.000000" as a local date (i.e. ISO 8601 format without a time zone), use something like:
// Parse y-m-dTh:m:s as local date and time
// since there is no timezone
function parseIsoLocal(s) {
var b = s.split(/\D/);
return new Date(b[0],b[1]-1,b[2],b[3],b[4],b[5],
((b[6]||'')+'000').slice(0,3));
}
// Convert string to Date
var d = parseIsoLocal('2016-02-21T02:14:39.000000');
// Show date and milliseconds since epoch
document.write(d + '<br>' + +d);
The above can easily be extended to treat the string as UTC, incorporate time zones and validate the input, but that doesn't seem to be required in this case.
Note that most browsers will parse the format in the OP, however some in use will not and, of those that will, some treat it as local and some as UTC. According to ISO 8601, it should be treated as local so that's what I've done.
I'm located in PST timezone and I want to be able to take the string "2014-01-01" and convert it into Unix time without "2014-01-01" getting converted to PST.
Here's what I'm doing:
Date.parse(new Date("2014-01-01"))
I'm getting the value 1388534400000 which is equivalent to Tue Dec 31 2013 16:00:00 GMT-0800 (Pacific Standard Time)
I want to take the date as "2014-01-01" and not convert it into PST before converting it into Unix time.
A few things:
The Date constructor returns a Date object, not a string. You shouldn't wrap it in a call to Date.parse.
If you want a unix timestamp, just call getTime().
var ts = new Date("2014-01-01").getTime();
Alternatively, you can parse the date string without creating a Date object at all.
var ts = Date.parse("2014-01-01");
The behavior of date parsing in JavaScript is implementation dependent. Most browsers will already interpret a yyyy-mm-dd string to be in UTC, due to the dashes (-). If you replace with with slashes (/), you'll see the string get interpreted as local time instead.
I think you're confused about the output. You said the timestamp was equivalent to PST, but that's just one representation. It's also equivalent to the UTC value you passed in. It's not getting converted in the input, it's being converted when you are converting the timestamp back to local time.
You can use a library like moment.js, which gives you full control of the input and output. This is usually the best option, but has the overhead of including a library in your application.
Another way to convert the specified date string to Unix time is as follows:
var str = "2014-01-01";
var parts = str.split('-');
parts[1] -= 1; // js numeric mos are 0-11
var ms = Date.UTC( parts[0], parts[1], parts[2] ); // parts: YYYY, MM, DD
var unix_time = ms/1000; // Unix time uses seconds
console.log("Unix time: " + unix_time);
Date.UTC() returns the number of milliseconds occurring since January 1, 1970 midnight up to the instant of the specified date, irrespective of any timezone. The script transforms the result into Unix time, i.e. seconds, by dividing the number of milliseconds by 1000.
After splitting the string into an array, the code adjusts the element containing the month, lest JavaScript mistake its value for March; JavaScript comprehends numeric months as ranging from 0-11, not 1-12. Next, the script passes the elements sequentially in accordance with the year, month, day parameters that Date.UTC requires. Although UTC() expects numbers for parameters, it accepts the numerical strings.
Note: if you first create a new date object and expect to use a UTC method -- that results in an error because it is a static method of JavaScript's Date Object.
You may check the validity of the UTC() return value, using the aforementioned variables ms and str, as follows:
console.log( new Date( str ).toUTCString( ms ));
The output: Wed, 01 Jan 2014 00:00:00 GMT
See live demo here)
Passing a date string to the Date constructor instead of the numerical parameters it expects affords an unexpected benefit; the date string is treated as if it's timezone is UTC, i.e. zero by the local date object. Once created, the local date object executes its toUTCString() method to attain the above-indicated result. The toString() method would also yield the same output, but it appends local timezone information.
I have a ISO date string as below
var startTimeISOString = "2013-03-10T02:00:00Z";
when I convert it to date object in javascript using below code, it returns
var startTimeDate = new Date(startTimeISOString);
output is
Date {Sun Mar 10 2013 07:30:00 GMT+0530 (India Standard Time)}
It sure converts the ISOString to date but it converts to local time since new Date() is client dependent. How to just convert iso date time string to date and time but not to local date-time..?
Thanks
According to MDN:
Differences in assumed time zone
Given a date string of "March 7, 2014", parse() assumes a local time
zone, but given an ISO format such as "2014-03-07" it will assume a
time zone of UTC. Therefore Date objects produced using those strings
will represent different moments in time unless the system is set with
a local time zone of UTC. This means that two date strings that appear
equivalent may result in two different values depending on the format
of the string that is being converted (this behavior is changed in
ECMAScript ed 6 so that both will be treated as local).
I have done like this and am now getting the exact time which is inside the ISO date string instead of the local time
var startTimeISOString = "2013-03-10T02:00:00Z";
var startTime = new Date(startTimeISOString );
startTime = new Date( startTime.getTime() + ( startTime.getTimezoneOffset() * 60000 ) );
This will give the same date time inside iso date string , the output here is
o/p
Date {Sun Mar 10 2013 02:00:00 GMT+0530 (India Standard Time)}
To sum up the conversation from tracevipin's post:
All Date objects are based on a time value that is milliseconds since 1970-01-01T00:00:00Z so they are UTC at their core. This is different to UNIX, which uses a value that is represents seconds since the same epoch.
The Date.prototype.toString method returns an implementation dependent string that represents the time based on the system settings and timezone offset of the client (aka local time).
If a UTC ISO8601 time string is required, the Date.prototype.toISOString method can be used. It's quite easy to write a "shim" for this methods if required.
Lastly, do not trust Date.parse to parse a string. Support for an ISO8601 format UTC string is specified in ES5, however it's not consistently implemented across browsers in use. It is much better to parse the string manually (it's not hard, there are examples on SO of how to do it) if wide browser support is required (e.g. typical web application).
Simple ISO8601 UTC time stamp parser:
function dateObjectFromUTC(s) {
s = s.split(/\D/);
return new Date(Date.UTC(+s[0], --s[1], +s[2], +s[3], +s[4], +s[5], 0));
}
and here's a shim for toISOString:
if (typeof Date.prototype.toISOString != 'function') {
Date.prototype.toISOString = (function() {
function z(n){return (n<10? '0' : '') + n;}
function p(n){
n = n < 10? z(n) : n;
return n < 100? z(n) : n;
}
return function() {
return this.getUTCFullYear() + '-' +
z(this.getUTCMonth() + 1) + '-' +
z(this.getUTCDate()) + 'T' +
z(this.getUTCHours()) + ':' +
z(this.getUTCMinutes()) + ':' +
z(this.getUTCSeconds()) + '.' +
p(this.getUTCMilliseconds()) + 'Z';
}
}());
}
This happens because date is printed using toString method which by default returns the date and time in local timezone. The method toUTCString will give you the string you need.
Date actually keeps the date as unix time in milliseconds and provides methods to manipulate it.
In vanilla javascript there isn't a way to create a date that assumes the local time of the ISO formatted string you give it. Here's what happens when you pass an ISO 8601 formatted string to javascript. I'm going to use a non UTC time as it illustrates the problem better than using an ISO formatted string:
var startTime = new Date("2013-03-10T02:00:00+06:00"). Note this could also be 2013-03-10T02:00:00Z or any other ISO-formatted string.
read the time, apply the offset and calculate milliseconds since 1970-01-01T00:00:00Z
You now have only milliseconds - you have lost all timezone info. In this case 1362859200000
All functions, apart from the ones that give you a UTC representation of that number, will use the timezone of the computer running the code to interpret that number as a time.
To do what the original poster wants, you need to.
parse the ISO string, interpret the offset ('Z' or '+06:00') as the timezone offset
store the timezone offset
calculate and store the ms since epoch, using the offset timezone offset
hold that offset
whenever attempting to make a calculation or print the date, apply the timezone offset.
This isn't trivial, and requires a complete interpretation of the 8601 spec. Way too much code to put here.
This is exactly what moment.js is designed to do. I strongly recommend using it. Using moment.js:
moment("2013-03-10T02:00:00Z").format()
"2013-03-10T02:00:00Z"
this will result in printing the ISO time of the original string, preserving the offset.
you can try moment js library https://momentjs.com
For my case, I had 2022-10-17T01:00:00 on my database. SO I need to format it to the 01:00:00 AM.
So here was my solution.
var date = "2022-10-17T01:00:00"
var timeFormat = moment(date ).format('HH:mm A');
output: 01:00:00 AM
it will return ISOdate
var getDate = () => {
var dt = new Date();
var off = dt.getTimezoneOffset() * 60000
var newdt = new Date(dt - off).toISOString()
return newdt.slice(0, 19)
}
Output