DOM:
<input id="myTextbox" type="datetime-local" />
Javascript (jQuery):
$('#myTextbox').val(new Date().toISOString());
Doesn't work. The format of input[type=datetime-local] is supposed to be ISO 8601, which is what javascript's Date.toISOString() returns.
Unfortunately, the previous answers did not work properly for me, because they suggest considering UTC time as my local time (which is, generally saying, incorrect).
For example, if my local time is 2021-03-10T01:50:55+0200, then date.toISOString() returns 2021-03-09T23:50:55Z, so I cannot just cut Z at the end, because for datetime-local I need local datetime 2021-03-10T01:50:55, NOT 2021-03-09T23:50:55.
So, the fixed code would be the following:
const d = new Date();
const dateTimeLocalValue = (new Date(d.getTime() - d.getTimezoneOffset() * 60000).toISOString()).slice(0, -1);
$('#myTextbox').val(dateTimeLocalValue);
That's why it works: we still use the trick of removing trailing "Z" from UTC's time format, but before doing it, we shift the time by our time zone offset (returning by date.getTimezoneOffset() in minutes) in the backward direction. After that, the shifted time, converted to UTC, provides the same date & time that our local. Of course, actually, the shifted time is a different moment, but we don't care as soon as its date & time in UTC matches our date & time in the local timezone.
With the example above, it works the following way:
shift local time by timezone offset in opposite direction (e.g. if it was UTC+2, then we make even further from UTC): 2021-03-10T01:50:55+0200 -> 2021-03-10T03:50:55+0200 (by - date.getTimezoneOffset() * 60000, because 1 minute is 60000 milliseconds)
return date&time values back by converting to UTC: 2021-03-10T03:50:55+0200 -> 2021-03-10T01:50:55Z (by .toISOString())
remove trailing Z to get real local time with the suited format for <input type="datetime-local"> (by .slice(0, -1))
If someone needs back transformation, from input value to js Date, then we just need to do the same steps in the reverse order:
const dateTimeLocalValue = $('#myTextbox').val();
const fakeUtcTime = new Date(`${dateTimeLocalValue}Z`);
const d = new Date(fakeUtcTime.getTime() + fakeUtcTime.getTimezoneOffset() * 60000);
console.log(d);
Any questions are welcome)
Update: this answer may set the date incorrectly (off by one day) based on your local time zone and time of day. See Maxim's answer for an explanation and a correct solution.
--
http://www.w3schools.com/jsref/jsref_toisostring.asp:
The toISOString() method converts a Date object into a string, using
the ISO standard.
The standard is called ISO-8601 and the format is:
YYYY-MM-DDTHH:mm:ss.sssZ
While ISO 8601 has some flexibility, the format of javascript's Date's toISOString() is exactly as shown above.
The 'Z' at the end means this is a UTC date. So, this representation includes timezone information. (Javascript dates are naturally in UTC time since they are internally represented as milliseconds since epoch.)
The format of HTML5 input with type=datetime-local must be ...
The following parts, in exactly the following order:
A date.
The literal string "T".
A time.
Example:
1985-04-12T23:20:50.52
1996-12-19T16:39:57
http://www.w3.org/TR/html-markup/input.datetime-local.html
This is still ISO 8601, but stricter, and it does not allow a timezone to be specified.
Luckily, removing the timezone is as easy as removing the trailing 'Z'.
var isoStr = new Date().toISOString();
$('#myTextbox').val(isoStr.substring(0,isoStr.length-1));
Date.toLocaleString can do the trick for you:
$('#myTextbox').val(new Date().toLocaleString("sv-SE", {
year: "numeric",
month: "2-digit",
day: "2-digit",
hour: "2-digit",
minute: "2-digit",
second: "2-digit"
}).replace(" ", "T"));
This will work even in browsers that don't support datatime-local like Firefox-desktop and Safari-desktop.
For more information on date-related-inputs to js-date conversions check this article that I wrote on the topic.
Use $('#myTextbox')[0].valueAsNumber = new Date().getTime().
HTMLInputElement interface also has valueAsDate property, but type=datetime-local doesn't support it unfortunately.
https://html.spec.whatwg.org/C/#input-type-attr-summary
For me, I do like this:
const d = new Date()
element.value = `${d.toLocaleDateString().split("/").reverse().join("-")} ${d.toLocaleTimeString()}`
Related
How do you check according to a timezone if you should modify the UTC time to -1 or +1 in Javascript? Need a function that takes in a timezone as string, and a time in UTC format and either add -1 or +1 depending on whether according to the timezone there's daylight savings or not and modify the UTC time appropriately. Is there a library that does this?
How do you check according to a timezone if you should modify the UTC time to -1 or +1 in Javascript?
For common offsets, the sign of the offset tells you whether to add or subtract from UTC to get local. So GMT+5:30 means add 5 hours and 30 minutes to UTC to get local.
POSIX offsets (such as those generated by ECMAScript's Date.prototype.getOffset) are the opposite, i.e. they indicate the time to add or subtract from local to get UTC, so in the above case the offset would be -5:30.
Need a function that takes in a timezone as string, and a time in UTC format and either add -1 or +1 depending on whether according to the timezone there's daylight savings or not and modify the UTC time appropriately.
Not all daylight saving offsets are 1 hour, some are 30 minutes. Typically places have a timezone name ending in "standard time" to indicate the normal offset, and a "daylight saving time" or "summer time" for when the daylight saving offset applies.
Offsets also depend on the date, so you need to provide a date and time like "2022-08-31T08:30:00Z".
Is there a library that does this?
Yes, there are many however library recommendations are off topic here. Research them, have a play, pick one you like. Then ask questions about a specific issue and library if you have any.
But you can also use POJS with either Date.prototype.toLocaleString or Intl.DatetimeFormat with suitable options and parsing the resulting string. You might also use Intl.DateTimeFormat.prototype.formatToParts:
let date = '2022-08-31T08:30:00Z';
let loc = 'Asia/Kolkata';
console.log(new Date(date).toLocaleString('en',{
hour: 'numeric',
hour12: false,
timeZone: loc,
timeZoneName: 'short'
}));
console.log(
new Date('2022-08-31T12:00:00Z').toLocaleString('en',{hour:'numeric', hour12:false, timeZone:'Asia/Kolkata', timeZoneName:'short'})
);
Note that the Intl.DateTimeFormat has numerous options for timeZoneName such as shortOffset that aren't widely supported yet so use with caution and stick with older options for wider compatibility.
This question is related to this question.
So if we construct a date using an ISO string like this:
new Date("2000-01-01")
Depending on what timezone we are in, we might get a different year and day.
I need to be able to construct dates in Javascript that that always have the correct year, day, and month indicated in a string like 2000-01-01, and based on the answer in one of the questions if we use back slashes instead like this:
const d = new Date("2000/01/01")
Then we will always get the right year, day, and month when using the corresponding date API methods like this:
d2.getDate();
d2.getDay();
d2.getMonth();
d2.getFullYear();
So I just wanted to verify that my understanding is correct?
Ultimately I need to be able to create Date instances like this for example:
const d3 = new Date('2010/01/01');
d3.setHours(0, 0, 0, 0);
And the time components should always be zero, and the year, month, and day should be the numbers specified in the string.
Thoughts?
I just did a quick test with this:
https://stackblitz.com/edit/typescript-eztrai
const date = new Date('2000/01/01');
console.log(`The day is ${date.getDate()}`);
const date1 = new Date('2000-01-01');
console.log(`The day is ${date1.getDate()}`);
And it logs this:
The day is 1
The day is 31
So it seems like using backslashes should work ...
Or perhaps using the year, month (0 based index), and day constructor values like this:
const date3 = new Date(2000, 0, 1);
date3.setHours(0, 0, 0, 0);
console.log(`The day is ${date3.getDate()}`);
console.log(`The date string is ${date3.toDateString()}`);
console.log(`The ISO string is ${date3.toISOString()}`);
console.log(`Get month ${date3.getMonth()} `);
console.log(`Get year ${date3.getFullYear()} `);
console.log(`Get day ${date3.getDate()} `);
NOTE
Runar mentioned something really important in the accepted answer comments. To get consistent results when using the Javascript Date API use methods like getUTCDate(). Which will give us 1 if the date string is 2000-01-01. The getDate() method could give us a different number ...
From the ECMA standard of the Date.parse method:
When the UTC offset representation is absent, date-only forms are interpreted as a UTC time and date-time forms are interpreted as a local time.
What is happening is that New Date() implicitly calls Date.parse on the string. The "2000-01-01" version conforms to a Date Time String Format with a missing offset representation, so it is assumed you mean UTC.
When you use "2000/01/01" as input the standard has this to say:
If the String does not conform to that format the function may fall back to any implementation-specific heuristics or implementation-specific date formats.
So in short the browser can do what they want. And in your case it assumes you mean the offset of the local time, so whichever offset you are located in gets added when you convert to UTC.
For consistent results, perhaps you want to take a look at Date.UTC
new Date(Date.UTC(2000, 0, 1))
If you need to pass in an ISO string make sure you include the time offset of +00:00 (is often abbreviated with z)
new Date("2000-01-01T00:00:00Z");
If you want to later set the date to something different, use an equivalent UTC setter method (e.g. setUTCHours).
When you retrieve the date, also make sure to use the UTC getter methods (e.g. getUTCMonth).
const date = new Date("2000-01-01T00:00:00Z");
console.log(date.getUTCDate());
console.log(date.getUTCMonth());
console.log(date.getUTCFullYear());
If you want to retrieve the date in a specific format you can take a look at Intl.DatTimeFormat, just remember to pass in timeZone: "UTC" to the options.
const date = new Date("2000-01-01T00:00:00Z");
const dateTimeFormat =
new Intl.DateTimeFormat("en-GB", { timeZone: "UTC" });
console.log(dateTimeFormat.format(date));
I have a date I want to convert based on their timezone.
For example, I want to set it in EST time (America/New_York)
2019-04-24 12:00:00
and if the user comes across the site from America/Los_Angeles, it will appear:
2019-04-24 09:00:00
I need to be able to return the hour, so in that example: 9.
I tried using https://github.com/iansinnott/jstz to determine their timezone and https://moment.github.io/luxon in hopes of handling the conversion w/o any luck.
I was testing by changing the timezone on my computer w/o any luck.
It sounds like you're asking to convert from a specific time zone to the user's local time zone (whatever it may be). You do not need time zone detection for that, but at present you do need a library. (Answers that suggest using toLocaleString with a time zone parameter are incorrect, as that function converts to a specific time zone, but cannot go the other direction.)
Since you mentioned Luxon, I'll provide a Luxon specific answer:
luxon.DateTime.fromFormat('2019-04-24 12:00:00', // the input string
'yyyy-MM-dd HH:mm:ss', // the format of the input string
{ zone: 'America/New_York'}) // the time zone of the input
.toLocal() // convert to the user's local time
.toFormat('yyyy-MM-dd HH:mm:ss') // return a string in the same format
//=> "2019-04-24 09:00:00"
This capability is also provided by other libraries, such as date-fns-timezone, js-Joda, or Moment-Timezone, but it is not yet something built in to JavaScript.
Converting date based on the time can be done like this. reference convert date to another time zone example snippet is under.
var usaTime = new Date().toLocaleString("en-US", {timeZone: "America/New_York"});
usaTime = new Date(usaTime);
console.log('USA time: '+usaTime.toLocaleString())
var usaTime = new Date().toLocaleString("en-US", {timeZone: "America/Los_Angeles"});
usaTime = new Date(usaTime);
console.log('USA time: '+usaTime.toLocaleString())
You could keep a list of timzeone identifiers and a list of their corresponding +/- number of hours with respect to your local time (which is returned by your time function).
Once you have a user's time zone, and you have extracted the current hour from the local timestamp simply look up the timezone in your list and use it's index to access the second list to find how many hours to add or subtract from the users time.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toLocaleString
var date = new Date(Date.UTC(2012, 11, 12, 3, 0, 0));
// toLocaleString() without arguments depends on the implementation,
// the default locale, and the default time zone
console.log(date.toLocaleString());
// → "12/11/2012, 7:00:00 PM" if run in en-US locale with time zone America/Los_Angeles
Or you can use getYear, getMonth, getDate, getHours, getMinutes, getSeconds to format your own representation of the date. These methods all return values according to the user's local timezone.
I think the question may need more clarification - my first impression was you refer to a date-time that you already have and serve from the server. Doesn't this problem boil down to the Date object being "user-timezone-aware"? or not? But it is (some methods are, to be exact)
Your date/time is 2019-04-24 12:00:00 EDT (i assume P.M.)
This means the Unix timestamp of this in milliseconds is 1556121600000
(i assume daylight is on for April so not pure EST but EDT and an offset of UTC-4:00)
When you call
console.log(new Date(1556121600000).getHours())
doesn't this return 9 as you suggest, for Javascript executed on a browser from America/Los_Angeles with PDT timezone?
As suggested at https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/getHours :
The getHours() method returns the hour for the specified date,
according to local time.
For sure, there is a lot of questions about Date objects and timezones but many of them are about converting the current time to another timezone, and others are not very clear about what they want to do.
I want to display the day, hour, minute etc. in an arbitrary timezone, in an arbitrary day. For example, I would like a function f(t, s) that:
given the timestamp 1357041600 (which is 2013/1/1 12:00:00 UTC) and the string "America/Los Angeles", would satisfy the comparison below:
f(1357041600, "America/Los Angeles") == "2013/01/01 04:00:00"
given the timestamp 1372680000 (2013/07/01 12:00:00 UTC), would satisfy the comparison below:
f(1357041600, "America/Los Angeles") == "2013/07/01 05:00:00"
will always behave this way even if the timezone in the browser is, let us say "Europe/London" or "America/São Paulo".
will always behave this way even if the time in the browser is, let us say 2014/02/05 19:32, or 2002/08/04 07:12; and
as a final restriction, will not request anything from the server side (because I'm almost doing it myself :) )
Is it even possible?
given the timestamp 1357041600 (which is 2013/1/1 12:00:00 UTC)
That appears to be seconds since the UNIX epoch (1970-01-01T00:00:00Z). Javascript uses the same epoch, but in milliseconds so to create a suitable date object:
var d = new Date(timestamp * 1000);
That will create a Date object with a suitable time value. You then need to determine the time zone offset using something like the IANA time zone database. That can be applied to the Date object using UTC methods. E.g. resolve the offset to minutes, then use:
d.setUTCMinutes(d.getUTCMinutes() + offset)
UTC methods can then be used to get the adjusted date and time values to create a string in whatever format you require:
var dateString = d.getUTCFullYear() + '/' + pad(d.getUTCMonth() + 1) + '/' ...
where pad is a function to add a leading zero to single digit values. Using UTC methods avoids any impact of local time zone offsets and daylight saving variances.
There are also libraries like timezone.js that can be used to determine the offset, however I have not used them so no endorsement is implied.
For JavaScript runtime environments that support the ECMAScript Internationalization API, and adhere to its recommendation of supporting the IANA time zone database, you can simply do this:
new Date(1357041600000).toLocaleString("en-US", {timeZone: "America/Los_Angeles"})
For other environments, a library is required. There are several listed here.
if dd = "2012-08-20 01:16:00";
converting this date to time-stamp (as in the following code)
var t = new Date(dd).getTime();
http://jsfiddle.net/userdude/DHxwR/
the result t = NaN why ?
According to ECMA-262 (§15.9.1.15, Date Time String Format, page 169), the only date string format required to be accepted is:
[+YY]YYYY[-MM[-DD]][THH:mm[:ss[.sss]]]Z
where Z is either Z (for UTC) or an offset consisting of either a + or a - followed by HH:mm. Any other formats that happen to be supported by a particular browser should not be relied upon, as continued support is not guaranteed.
Therefore, replace the space with a T and append either a Z, or a fixed time zone offset before passing it to the Date constructor. For example, if the date and time are in the UTC+8 zone:
var dd = "2012-08-20 01:16:00";
var t = new Date(dd.replace(' ', 'T') + '+08:00').getTime();
This will return the number of milliseconds from January 1, 1970, midnight UTC, to the date you have specified, treated as either universal time (if you appended Z) or a time local to the fixed time zone offset that you specify.
Please note that this will act differently in that the date is not simply treated as time local to the user's system time zone as your question's example does. However, I can't think of a situation where doing that would be useful, because you'd get different results depending on the user's configuration — but in reality, the time difference between two dates is always the same no matter where you are.
Try to use a space or comma between the year, month, and day values.
It's simple:
+(new Date("2012-08-20 01:16:00"));