Moment Display Date according to ISO-8601 Timezone Offset - timezone

I am getting a ISO-8601 date string from an API response as follows :
var x1 = 2022-06-22T05:30:00+05:30
or it could be
var x2 = 2022-06-22T08:30:00-05:00
Irrespective of browser timezone I should display the dates as
X1 - 2022-06-22 05:30:30 IST
X2 - 2022-06-22 08:30:00 EST
How can i parse timezone from the offset like -05:00 or +05:30 using moment or luxon?
I tried moment.tz(timestamp) but it defaults to UTC since it needs the second argument.

So i did a bit more digging.
Logically what i want is not possible.
Many timezones shares UTC offset. Hence, there could be ambiguity, if we try to convert an offset to a TimeZone without any other additional info
Hence, I am opting for a solution, where my API response sends a timezone metadata for each date/time field. (I have lat/long info to convert in Tz in my backend)
In front End, i will simply use the timezone info to format my moment object into a desired date-time String.
For example
const timestring = '2022-06-22T00:00:00+00:00';
const timezoneName = "America/Chicago" ;
moment.tz(timestring, timezoneName).format('YYYY-DD-MM hh:mm:ss z');
// Output: 2022-06-21 07:00:00 CDT
Source : https://stackoverflow.com/tags/timezone/info

Related

Transform Epoch UTC to String EST using momentjs

I have two input variables: an epoch time in UTC time zone and the name of the actual time zone. How do I get a formatted day/time using moment.js that would take in account the DST changes. I tried this code but it doesn't do the trick. What am I doing wrong, please?
var abs_time = 1611188219.277; // this is UTC coresponding to 1/21/2021 18:31:37 UTC
var timezone = "America/New_York"; // this the actual time zone
var mom = moment(abs_time * 1000).format();
var date_time = moment.tz(mom, timezone).format('ddd, MMM DD YYYY - HH:mm');
console.log(date_time);
//actual result: Thu, Jan 21 2021 - 18:31
//desired result: Thu, Jan 21 2021 - 13:31 - in the summer this should only be 4 hour difference
First, 1611188219.277 actually corresponds to 2021-01-21T00:16:59.277Z, not the time you gave in your question (assuming it is a Unix timestamp with seconds precision). This can be seen with the following code:
const d = new Date(1611188219.277 * 1000);
const s = d.toISOString();
console.log(s);
You can get the equivalent local time in a specific time zone without any libraries, as long as you're satisfied with the output produced by the toLocaleString function.
const d = new Date(1611188219.277 * 1000);
const s = d.toLocaleString(undefined, { timeZone: 'America/New_York' });
console.log(s);
Note that undefined in the above code will use the browser's current language. If you want a specific language, you could pass its language code there instead (such as en or en-US, etc.)
In general, due to its project status, you should avoid using Moment unless it's already being used in an existing project. If however, you must use Moment and Moment-TimeZone for this, you can do the following to get the same result:
const m = moment.tz(1611188219.277 * 1000, 'America/New_York');
const s = m.format('ddd, MMM DD YYYY - HH:mm');
console.log(s);
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.29.1/moment.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment-timezone/0.5.32/moment-timezone-with-data-10-year-range.min.js"></script>
I used the same format from your question, but of course you could change this as desired.
You might also consider using Luxon (the successor to Moment), or Date-fns, or several other libraries.
And yes, all of the above will correctly take daylight saving time into account.

Trouble subtracting time from a moment

I am working on a project that uses a different timezone than the one I currently live in:
moment.tz.add("Asia/Seoul|LMT KST JST KST KDT KDT|-8r.Q -8u -90 -90 -9u -a0|0123141414141414135353|-2um8r.Q 97XV.Q 1m1zu kKo0 2I0u OL0 1FB0 Rb0 1qN0 TX0 1tB0 TX0 1tB0 TX0 1tB0 TX0 2ap0 12FBu 11A0 1o00 11A0|23e6")
Then formatted it as such:
const kST = moment().tz('Asia/Seoul').format("HH:mm");
Now I want to be able to subtract a year from that. Looking at examples of how to do that I found something like var foo = moment(blah, "HH:mm).subtract(1, "years")
I assumed that since I already defined the moment with the 'const kST' I could simply substitute "kST" for "moment" as such:
const firstTimeConverted = kST(firstBus, "HH:mm").subtract(1, "years");
Unfortunately that doesn't work. Any thoughts how I might do this would be much appreciated.
In your code, kST isn't a function - it's a string. The format returns a string formatted as specified.
You probably want:
const firstTimeConverted = moment.tz(firstBus, "HH:mm", `Asia/Seoul`).subtract(1, "years");
This will parse the string in your firstBus variable in HH:mm format (such as "23:45"), and interpret as belonging to the Asia/Seoul time zone on the current date there. Then it will subtract a year and return the result as a moment object. If you want a string, you would then need to call the format function.

How to parse Date in IST format in Golang?

time.Date(t.Year(), t.Month(), time.Now().Day(), 10, 0, 0, 0, time.UTC)
I want to set dateTime of 10:00:00 AM in IST format in golang.
It depends on the format of the time you have at hand. Go has some standard time formats ready as consts in the time package, but you can specify your own standard if it's custom. Regarding the time zone, you can parse or output a time in a specific time zone. Here is an example of parsing a time string in IST, and outputting it as UTC. It's not clear from your question what is your precise problem but I hope this helps:
// First, we create an instance of a timezone location object
loc, _ := time.LoadLocation("Asia/Kolkata")
// this is our custom format. Note that the format must point to this exact time
format := "Jan _2 2006 3:04:05 PM"
// this is your timestamp
timestamp := "Jun 25 2015 10:00:00 AM"
// now we parse it, considering it's in IST
t, err := time.ParseInLocation(format, timestamp, loc)
// printing it prints it in IST, but you can set the timezone to UTC if you want
fmt.Println(t, err)
// example - getting the UTC timestamp
fmt.Println(t.UTC())

Getting current time of day down to milliseconds error

I have been attempting to access the time of day in hour:minute:second format however all that these
println(CFTimeZoneCopySystem())
println(CFTimeZoneCopyDefault())
println(gettimeofday)
println(CACurrentMediaTime)
print are
America/New_York (EDT) offset -14400 (Daylight)
America/New_York (EDT) offset -14400 (Daylight)
(Function)
(Function)
I don't understand why these are simply printing out "(function)" and I am also unsure as to what time format 14400 is. I want to be able to access something that would be accurate across bluetooth devices. so that is why I would prefer to access milliseconds. I know there was another question similar to this one however I do not think they received this article as well as I do not understand objective-C
You can use the code below:
let formatter = NSDateFormatter()
//formatter.timeZone = NSTimeZone(forSecondsFromGMT: 0) // you can set GMT time
formatter.timeZone = NSTimeZone.localTimeZone() // or as local time
formatter.dateFormat = "HH:mm:ss.SSS"
println(formatter.stringFromDate(NSDate()))
Output: "05:57:26.123"

Unix time with NSDate reveals erroneous results

I live in Denmark (UTC + 1 ) and I am working with a webapi that sends my app a unix timestamp since 1970-1-1 00:00:00. The time is in the future (train depatures)
If I check the timestamp in Numbers or Excel it gives me the correct time
To calculate the number of minutes until the train departures I do like this:
let unixTimeTrainDeparture = 1419327780 //(or some time in the future)
let unixRightNow = NSDate().timeIntervalSince1970
let minutesToDeparture = (Int(unixTimeTrainDeparture) - Int(unixRightNow))/60
However this gives 60 minutes too much?
And If I do a
let dateTest = NSDate(string: "1970-01-01 00:00:00 +0000")!
will give me 1 jan 1970 :01:00:00 +0000
This does not make sense to me. It is like the timeIntervalSince1970 gives me 3600 sec too less, as it starts from 1970-1-1 01:00 rather than 00:00? It this a bug or is it the way it should be?
I can correct the time by using the
let tz = NSTimeZone.defaultTimeZone()
let seconds = tz.secondsFromGMTForDate(NSDate())
and then subtracting the seconds from my result. However, what happens when we move into summer time?
timeIntervalSince1970 always gives the time in GMT. Your unixTimeTrainDeparture is probably the time in GMT+1, which explains the 60 minute difference (or 120 minutes in summer time). Same goes with the string conversion - you input a GMT time and it outputs the date in whatever timezone you have configured (I'm guessing your computer's setting is GMT+1 as well).
When working with timezones, always start with GMT/UTC and don't do any timezone conversions until displaying the date to the user.
Do you have any control over the web API? If so - configure it to send GMT instead. This should completely avoid time zone and daylight savings issues.
If you cannot do that you will have to implement some function to convert the timestamp yourself, accounting for the possibility that a future timestamp could be in a different timezone (eg daylight savings). NSTimeZone might be very useful for this!
Hope I have understood your problem correctly!
Edit, added example that should handle DST:
// Date far in the future in DST, replace this
let unixTimeTrainDeparture = NSDate(timeIntervalSince1970: 1436447418)
let now = NSDate()
// Assume unixTimeTrainDeparture is in the Copenhagen timezone
let tz = NSTimeZone(name: "Europe/Copenhagen")
// This is 3600 in non-DST, otherwise 7200
let offset = tz!.secondsFromGMTForDate(unixTimeTrainDeparture)
let realUnixTimeTrainDeparture = Int(unixTimeTrainDeparture.timeIntervalSince1970) - offset
let timeToDeparture = realUnixTimeTrainDeparture - Int(now.timeIntervalSince1970)

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