date-fns | How do I format to UTC

Question

Problem

It looks like when I use the format() function, it automatically convert the original UTC time into my timezone (UTC+8). I have been digging through their docs for hours and couldn't seem to find a way to default it to UTC time.

import { parseISO, format } from "date-fns";

const time = "2019-10-25T08:10:00Z";

const parsedTime = parseISO(time);
console.log(parsedTime); // 2019-10-25T08:10:00.000Z

const formattedTime = format(parsedTime, "yyyy-MM-dd kk:mm:ss");
console.log(formattedTime); // 2019-10-25 16:10:00 <-- 8 HOURS OFF!!

I have tried to use the package data-fns-tz and use something like

format(parsedTime, "yyyy-MM-dd kk:mm:ss", {timeZone: "UTC"});

still no luck.

Please help!

Expected Output

2019-10-25 08:10:00

Actual Output

2019-10-25 16:10:00

Solution 1

I would suggest using the built-in Date util:

const date = new Date("2019-10-25T08:10:00Z");
const isoDate = date.toISOString();

console.log(`${isoDate.substr(0, 10)} ${isoDate.substr(11, 8)}`);

Outputs:

2019-10-25 08:10:00

Not a general solution for any format, but no external libraries required.

Solution 2

You were almost there. This works for me:

import { parseISO } from "date-fns";
import { format, utcToZonedTime } from "date-fns-tz";

const time = "2019-10-25T08:10:00Z";

const parsedTime = parseISO(time);
console.log(parsedTime); // 2019-10-25T08:10:00.000Z

const formatInTimeZone = (date, fmt, tz) =>
  format(utcToZonedTime(date, tz), 
         fmt, 
         { timeZone: tz });

const formattedTime = formatInTimeZone(parsedTime, "yyyy-MM-dd kk:mm:ss xxx", "UTC");
console.log(formattedTime); // 2019-10-25 08:10:00 +00:00

Behind the scenes

The date-fns[-tz] libraries stick to the built-in Date data type that carries no TZ info.
Some functions treat it as a moment-in-time, but some like format treat it more like a struct of calendaric components — year 2019, ..., day 25, hour 08, ....

Now the trouble is a Date is internally only a moment in time. Its methods provide a mapping to/from calendaric components in local time zone.

So to represent a different time zone, date-fns-tz/utcToZonedTime temporarily produces Date instances which represent the wrong moment in time — just to get its calendaric components in local time to be what we want!

And the date-fns-tz/format function's timeZone input affects only the template chars that print the time zone (XX..X, xx..x, zz..z, OO..O).

See https://github.com/marnusw/date-fns-tz/issues/36 for some discussion of this "shifting" technique (and of real use cases that motivated them)...
It's a bit low-level & risky, but the specific way I composed them above — formatInTimeZone() — is I believe a safe recipe.

Solution 3

Note
The following solution will not work for all time zones, so if timezone accuracy is critical for your application you might want to try something like the answer from Beni. See this link for more info

I had the exact same question today and did some research to see if anyone has come up with anything better since this question was posed. I came across this solution which fit my needs and stylistic preference:

import { format, addMinutes } from 'date-fns';

function formatDate(date) {
  return format(addMinutes(date, date.getTimezoneOffset()), 'yyyy-MM-dd HH:mm:ss');
}

Explanation

getTimezoneOffset returns the number of minutes needed to convert that date to UTC. In PST (-0800 hours) it would return 480 whereas for somebody on CST (+0800 hours) it would return -480.

Solution 4

I had the same problem. What I do is remove the timezone from the ISO string and then use that time with date-fns:

let time = "2019-10-25T08:10:00Z".slice(0, -1)

The above is a time with no time zone, and because there is no timezone date-fns assumes the local timezone, so when you do:

format(parseISO(time), 'h:mm a')

you get: 8:10 AM, or whatever format you prefer. You just have to be careful with the string that you are slicing. If its always the same format then it should work.

Solution 5

I did something like this using date/fns and native date methods

import format from 'date-fns/format';
import parseISO from 'date-fns/parseISO';

export const adjustForUTCOffset = date => {
  return new Date(
    date.getUTCFullYear(),
    date.getUTCMonth(),
    date.getUTCDate(),
    date.getUTCHours(),
    date.getUTCMinutes(),
    date.getUTCSeconds(),
  );
};

const formatDate = (dateString) = > {
    const date = parseISO(dateString);
    const dateWithOffset = adjustForUTCOffset(date)
    return format(dateWithOffset, 'LLL dd, yyyy HH:mm')
}

View more solutions

Comments

[Patrick Mao]

Thank for the reply, but sadly, the reason I chose to use a library is that I need to do calculation on dates :(

[Matt Johnson-Pint]

You can still use date-fns for everything except that last part for output. It does return, afterall, Date objects.

[Patrick Mao]

Looks like this is the only way out if I want to use date-fns. Excellent answer!

[tilo]

You should note that this solution does not work for all timezones, as pointed out in the thread you referred to: github.com/date-fns/date-fns/issues/1401#issuecomment-621897‌​094

[Komal Khatkole]

@Sherwin, for me instead of doing +5.30 , it is doing -5.30 . So how should I correct it.?

[Sherwin F]

@KomalKhatkole getTimezoneOffset returns the number of minutes needed to convert your local time to a UTC time, so if your offset is +5:30 it will return -330 minutes. Is this what's happening?

[nerrons]

For anyone wondering if this is a hack or not -- It's in fact the official way of formatting to a certain timezone, including UTC: npmjs.com/package/date-fns-tz#format

[Mitchell Brooks]

I am stuck on 1.30.1 for now and this worked for me

[ufk]

it is ok to tell you that i love you ? :) you saved my project thanks

[Beni Cherniavsky-Paskin]

But the jury is still out on whether the official way is a hack or not :-D Specifically I'm worried about calendaric times that do not exist in some time zones e.g. bbc.com/news/world-asia-16351377 — if your local TZ is Samoa, no timestamp maps to 30 December 2011, so if you want to format that date from another TZ I'm not sure it'd work.

[graup]

I like this solution. It's correct and a one-liner.

[User 1058612]

Worked great, thank you.

[User 1058612]

This works for me. Took me a few tries before I realized that the format import must come from date-fns-tz and not the core date-fns, but worked after that.

[Alex Buznik]

The parsedTime from your snippet returns InvalidDate

[cyberfly]

The answer is partially correct, but he missed the usage of parseISO. I edited the answer ` const parsedTime = parseISO(new Date(Date.UTC(time))); `