I have a function in Java to convert an Epoch date to ISO 8601, but I've come across the need to do it in Javascript. I have it somewhat working in JS but it needs to be localized to the timezone.
Java version:
public static String epochToIso8601(long time, String Zone) {
String format = "yyyy-MM-dd'T'HH:mm:ssX";
TimeZone timeZone = TimeZone.getTimeZone(Zone);
SimpleDateFormat sdf = new SimpleDateFormat(format, Locale.getDefault());
sdf.setTimeZone(timeZone);
return sdf.format(new Date(time));
}
Param1: -157737600000
Param2: PST
Output: 1965-01-01T00:00:00-08
My attempt in Javascript:
function epcov(epoch, timezone)
{
var someValueNum = Number(epoch);
var s = new Date(someValueNum);
return s.toISOString();
}
Essentially I want the same thing that's coming out of Java, but it's outputting: 1965-01-01T08:00:00.000Z
By the way, I'm already splitting the date and time up from something that looks like this, so if there is a better to just pass in the following as one string and let Javascript parse it, that would be amazing:
/Date(-157737600000-0800)/
We can convert the string /Date(-157737600000-0800)/ to a unix time (in ms), and a UTC offset in HHMM using String.match().
The HHMM UTC offset can then be converted to a UTC offset in milliseconds by multiplying the HH value by 3600000 and the MM value by 60000.
We then create a new Date object using the unix time and offset values, since we know the exact offset at that point in time.
We then format using Date.toISOString() and replace the 'Z' UTC offset timezone value with the actual UTC offset string (e.g. '-08:00').
function parseAndFormatDate(date) {
const [,millis, offset] = date.match(/([+\-]+\d+)([+\-]+\d+)/);
const offsetMillis = (offset.slice(0, 1) + '1') * (offset.slice(1, 3) * 3600000 + offset.slice(-2) * 60000);
const formattedOffset = offset.slice(0, 3) + ':' + offset.slice(-2);
return new Date(+millis + offsetMillis).toISOString().replace('Z', formattedOffset);
}
console.log(parseAndFormatDate('/Date(-157737600000-0800)/'));
console.log(parseAndFormatDate('/Date(+1664271413000+0100)/'));
.as-console-wrapper { max-height: 100% !important; }
I hope this helps you in some way.
JS doesn't have good (any?!) support for exporting an ISO 8601 string in a specified time zone. So you have to construct the string yourself, manually.
The use of the Swedish locale is to get an ISO 8601-like basis from which to pull the elements of the date time. Unfortunately there is no ISO 8601 formatting locale.
Note that the following will only reliably work with IANA timezone names because timezone abbreviations (PST, CST, BST) can be ambiguous. For example: V8 will accept 'PST' but SpiderMonkey will not.
// Get wall clock date at the specified tz in IS0 8601
const getISO8601Date = (d, timeZone) =>
d.toLocaleString('sv-SE', { timeZone, dateStyle: 'short'})
// Get wall clock time at the specified tz in IS0 8601
const getISO8601Time = (d, timeZone) =>
d.toLocaleString('sv-SE', { timeZone, timeStyle: 'medium'})
// Get time zone offset in specified tz in IS0 8601
const getISO8601TimeZoneOffset = (d, timeZone) => {
const s = d.toLocaleString('sv-SE', { timeZone, timeZoneName: 'longOffset' })
const result = /GMT(?<offset>[+−]\d\d:\d\d)/.exec(s) // Use regexp to pull out offset
return result ? result.groups.offset : 'Z'
}
// Put together an ISO 8601 string representing the wall clock at the specified date, in the specified timezone
const getISO8601Dtg = (instant, timeZone) => {
const d = new Date(instant)
return `${getISO8601Date(d, timeZone)}T${getISO8601Time(d, timeZone)}${getISO8601TimeZoneOffset(d, timeZone)}`
}
// Only reliably accepts IANA timezone names eg. 'America/Los_Angeles'
console.log(getISO8601Dtg(-157737600000, 'America/Los_Angeles')) // 1965-01-01T00:00:00−08:00
Relevant.
Related
I'm trying to convert the time ( time alone ) from a known timezone to my local timezone with Moment.js.
I wrote the following function and, I am getting invalidDate as the output.
const convertToLocalTime = (time, tz) => {
const t = moment.tz(time, tz)
const localTime = t.local()
}
time is just time; without any date eg: 10:06 am and,
tz is a timezone string for eg: Europe/Berlin
What am I doing wrong?
See Parsing in Zone:
The moment.tz constructor takes all the same arguments as the moment constructor, but uses the last argument as a time zone identifier.
Since your input (10:06 am) is not in ISO 8601/RFC 2822 recognized format (see moment(String) docs), you have to pass format parameter as shown in moment(String, String).
Here a live sample:
const convertToLocalTime = (time, tz) => {
const t = moment.tz(time, 'hh:mm a', tz)
const localTime = t.local()
return localTime;
}
const res = convertToLocalTime("10:06 am", 'Europe/Berlin');
console.log( res.format('hh:mm a') );
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.24.0/moment.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment-timezone/0.5.14/moment-timezone-with-data-2012-2022.min.js"></script>
When I do this:
new Date('4/7/2018').toISOString();
I get: "2018-04-06T22:00:00.000Z"
How can I get an ISO string but without the date changing from 7 to 6? I basically want the same date, month and year.
Use 2018Z in your year field:
var res = new Date('4/7/2018Z').toISOString();
console.log(res);
I think this is to do with the locale of the machine (i.e you're on gmt+2 so 4/7/2018 at 00:00:00 is indeed 2018-04-06T22:00:00.000Z)
You could do new Date('4/7/2018 GMT').toISOString();
Date strings do not have a timezone. Using the built-in parser for any format other than the one specified in ECMA-262 (a limited subset of ISO 8601) is implementation dependent and should not be used, see Why does Date.parse give incorrect results?
A couple of options are to parse the string as UTC values and then use toISOString and remove the trailing Z, or you can just reformat the string, e.g.
var s = '4/7/2018';
// Parse string in m/d/y format and return
// in ISO 8601 format
function parseDMY(s) {
var b = s.split(/\D/);
return new Date(Date.UTC(b[2],b[0]-1,b[1])).toISOString().slice(0,19);
}
console.log(parseDMY(s));
function reformatDate(s) {
var b = s.split(/\D/);
function z(n){return (n<10?'0':'')+n};
return `${b[2]}-${z(b[0])}-${z(b[1])}T00:00:00`;
}
console.log(reformatDate(s));
But really, if you just have a date, it should be left as just a date, so:
var s = '4/7/2018';
// Assume date is M/D/Y
function reformatDate(s) {
var a = s.split(/\D/).map(n=>(n<10?'0':'')+n);
return a[2]+'-'+a[0]+'-'+a[1];
}
console.log(reformatDate(s));
I have a list of list of string dates like this: '17/12/2017 19:34'. They are CET dates.
How can I transform it to the user's browser date?
I'm doing this:
const tzGuess = moment.tz.guess()
export const toTimeZone = (time) => {
const format = 'DD/MM/YYYY HH:mm'
return moment(time, format).tz(tzGuess).format(format)
}
console.log(toTimeZone('17/12/2017 19:34', tzGuess))
but how can I say to moment that the date I'm passing at first is a CET one?
Thanks!
You can use moment.tz function for parsing time string using a given timezone (e.g. 'Europe/Madrid').
The issue is: what do you mean with CET? If your input has fixed UTC+1 offset (like Central European Time), then you can use RobG's solution. If you have to consider both CET and CEST, I think that the best soution is to use moment.tz.
Here a live code sample:
const tzGuess = moment.tz.guess()
const toTimeZone = (time) => {
const format = 'DD/MM/YYYY HH:mm'
return moment.tz(time, format, 'Europe/Madrid').tz(tzGuess).format(format)
}
console.log(toTimeZone('17/12/2017 19:34', tzGuess))
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.19.4/moment.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment-timezone/0.5.13/moment-timezone-with-data-2012-2022.min.js"></script>
A great resource about timezone is the timezone tag info page.
Without moment.js, parse the string to a Date, treating it as UTC, then adjust for the CET offset (+0100). You can then format it using local time values for the client:
// Parse date in format DD/MM/YYYY HH:mm
// Adjust for CET timezone
function parseCET(s) {
var b = s.split(/\D/);
// Subtract 1 from month and hour
var d = new Date(Date.UTC(b[2], b[1]-1, b[0], b[3]-1, b[4]));
return d;
}
var s = '17/12/2017 19:34';
console.log(parseCET(s).toString());
However, if the time needs to observe daylight saving (CEST) for the source time stamp, you'll need to account for that.
I am trying to convert a UTC date to local time on my node server and finally return the localized time in the format of hh:mm:ss (not using Moment JS). I'm passing in the timezone offset from the client to Node, which is GMT-6.
My original time is: 2017-05-05T00:25:11.378Z
// ISOTimeString = `2017-05-05T00:25:11.378Z`
// offsetInMinutes = 360; (GMT - 6)
function isoDateToLocalDate(ISOTimeString, offsetInMinutes) {
var newTime = new Date(ISOTimeString);
return new Date(newTime.getTime() - (offsetInMinutes * 60000));
}
The localized time is 2017-05-04T18:25:11.378Z, which is correct (2017-05-05T00:25:11 - 6 hours = 2017-05-04T18:25:11).
// localIsoDate: 2017-05-04T18:25:11.378Z Date object
function formatTime(localIsoDate) {
var hh = localIsoDate.getHours();
var mm = localIsoDate.getMinutes();
var ss = localIsoDate.getSeconds();
return [hh, mm, ss].join(':');
}
// formatted: 12:25:11
The problem is, while still on the server, when I try to format into hh:mm:ss, it subtracts another 6 hours, giving me 12:25:11. I don't want to convert again, I simply want to format and display 18:25:11 from the already localized time.
How can I do this?
Note: Keep in mind I do not have the option to convert timezones after it's passed back to the client in my case.
The isoDateToLocalDate seems to be OK, however in the formatTime you need to use UTC methods, otherwise you are getting the host local values, not the adjusted UTC values.
Also, in ISO 8601 terms (and general convention outside computer programming), an offset of 360 represents a timezone of +0600, not -0600. See note below.
// ISOTimeString = 2017-05-05T00:25:11.378Z
// ECMAScript offsetInMinutes = 360; (GMT-0600)
function isoDateToLocalDate(ISOTimeString, offsetInMinutes) {
var newTime = new Date(ISOTimeString);
return new Date(newTime.getTime() - (offsetInMinutes * 60000));
}
// localIsoDate: 2017-05-04T18:25:11.378Z Date object
function formatTime(localIsoDate) {
function z(n){return (n<10?'0':'')+n}
var hh = localIsoDate.getUTCHours();
var mm = localIsoDate.getUTCMinutes();
var ss = localIsoDate.getUTCSeconds();
return z(hh)+':'+z(mm)+':'+z(ss);
}
var timeString = '2017-05-05T00:25:11.378Z';
var offset = 360;
console.log(formatTime(isoDateToLocalDate(timeString, offset)))
ECMAScript timezone signs are the reverse of the usual convention. If the client timezone offset is +0600 then their host will show -360.
How can I convert UTC date-time string (e.g. 2011-03-29 17:06:21 UTC) into Epoch (milliseconds) in javascript?
If this is not possible, is there any way to compare (like <, >) UTC date time strings?
Note that UTC date strings can be compared lexicographically, like strings, since the higher order values appear leftmost in the string.
var s1 = '2011-03-29 17:06:21 UTC'
, s2 = '2001-09-09 01:46:40 UTC';
s1 > s2; // => true
s2 > s1; // => false
You can extract the date fields from your example string and return the number of milliseconds by using the Date.UTC method:
var getEpochMillis = function(dateStr) {
var r = /^\s*(\d{4})-(\d\d)-(\d\d)\s+(\d\d):(\d\d):(\d\d)\s+UTC\s*$/
, m = (""+dateStr).match(r);
return (m) ? Date.UTC(m[1], m[2]-1, m[3], m[4], m[5], m[6]) : undefined;
};
getEpochMillis('2011-03-29 17:06:21 UTC'); // => 1301418381000
getEpochMillis('2001-09-09 01:46:40 UTC'); // => 1000000000000
Using datejs will help you convert the UTC string to a Date object. After that it's simply a matter of calling .getTime() on the date object to get the milliseconds.
this is how to do it. No nonsese. Date.UTC accepts a UTC timestamp and returns epoch
var epoch_date = Date.UTC(year,mon,day,hours,min,sec,milisec);
As long as the datetime string is something unambiguous like an ISO8601-ish format (i.e. not MM/DD/YYYY vs DD/MM/YYYY), you can just use the Date constructor to parse it and then Math.floor:
Math.floor(new Date('2011-03-29 17:06:21 UTC') / 1000); // => 1301418381
You could use getDateFromFormat(dateValue, dateFormat) (available here) like so:
getDateFromFormat("2011-03-29 17:06:21","yyyy-MM-dd HH:mm:ss")
It returns the epoch time in milliseconds.