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zonedTimeToUtc() change to summer time at the wrong hour

See original GitHub issue

The change from standard PST (-08:00) to summer time PDT (-07:00) in America/Los_Angeles occurred at 2am on March 8, 2020 local time. As you can see in the test below, moment handles this correctly by converting 2020-03-08 02:00 local time as well as 2020-03-08 03:00 local time to the same ISO date (2020-03-08T10:00:00.000Z).

zonedTimeToUtc however does not change to summer time until 2020-03-08 10:00 local time, which is 8 hours too late. Interestingly 8 hours is the same as the regular PST offeset, so perhaps zonedTimeToUtc switches over to summertime based on UTC instead of local time, just an idea.

import { zonedTimeToUtc } from 'date-fns-tz';
import moment from 'moment';
import 'moment-timezone';

const times = [
  '2020-03-08 02:00', //  true 2020-03-08 02:00 d 2020-03-08T10:00:00.000Z m 2020-03-08T10:00:00.000Z
  '2020-03-08 03:00', // false 2020-03-08 03:00 d 2020-03-08T11:00:00.000Z m 2020-03-08T10:00:00.000Z
  '2020-03-08 04:00', // false 2020-03-08 04:00 d 2020-03-08T12:00:00.000Z m 2020-03-08T11:00:00.000Z
  '2020-03-08 05:00', // false 2020-03-08 05:00 d 2020-03-08T13:00:00.000Z m 2020-03-08T12:00:00.000Z
  '2020-03-08 06:00', // false 2020-03-08 06:00 d 2020-03-08T14:00:00.000Z m 2020-03-08T13:00:00.000Z
  '2020-03-08 07:00', // false 2020-03-08 07:00 d 2020-03-08T15:00:00.000Z m 2020-03-08T14:00:00.000Z
  '2020-03-08 08:00', // false 2020-03-08 08:00 d 2020-03-08T16:00:00.000Z m 2020-03-08T15:00:00.000Z
  '2020-03-08 09:00', // false 2020-03-08 09:00 d 2020-03-08T17:00:00.000Z m 2020-03-08T16:00:00.000Z
  '2020-03-08 10:00', //  true 2020-03-08 10:00 d 2020-03-08T17:00:00.000Z m 2020-03-08T17:00:00.000Z
];

times.forEach((t) => {
  const d = zonedTimeToUtc(t, 'America/Los_Angeles').toISOString();
  const m = moment.tz(t, 'America/Los_Angeles').toDate().toISOString();

  console.log(d === m, t, 'd', d, 'm', m);
});

Issue Analytics

State:
Created 3 years ago
Comments:5 (2 by maintainers)

Top GitHub Comments

2reactions

dkozickiscommented, Mar 30, 2020

Huh, you’re correct @lirbank … Either something wrong with my environment or with my perception of time 😄

Some day date-fns will have TZ functionality built-in, some day …

0reactions

lirbankcommented, Mar 29, 2020

For reference, these all pass, regardless if 2.11.0 or 2.11.1 is used:

test('parseISO', () => {
  expect(parseISO('2020-03-08 00:00').toString()).toEqual(
    'Sun Mar 08 2020 00:00:00 GMT-0800 (Pacific Standard Time)',
  );
  expect(parseISO('2020-03-08 01:00').toString()).toEqual(
    'Sun Mar 08 2020 01:00:00 GMT-0800 (Pacific Standard Time)',
  );
  expect(parseISO('2020-03-08 02:00').toString()).toEqual(
    'Sun Mar 08 2020 03:00:00 GMT-0700 (Pacific Daylight Time)',
  );
  expect(parseISO('2020-03-08 03:00').toString()).toEqual(
    'Sun Mar 08 2020 03:00:00 GMT-0700 (Pacific Daylight Time)',
  );
  expect(parseISO('2020-03-08 04:00').toString()).toEqual(
    'Sun Mar 08 2020 04:00:00 GMT-0700 (Pacific Daylight Time)',
  );
  expect(parseISO('2020-03-08 05:00').toString()).toEqual(
    'Sun Mar 08 2020 05:00:00 GMT-0700 (Pacific Daylight Time)',
  );
  expect(parseISO('2020-03-08 06:00').toString()).toEqual(
    'Sun Mar 08 2020 06:00:00 GMT-0700 (Pacific Daylight Time)',
  );
  expect(parseISO('2020-03-08 07:00').toString()).toEqual(
    'Sun Mar 08 2020 07:00:00 GMT-0700 (Pacific Daylight Time)',
  );
  expect(parseISO('2020-03-08 08:00').toString()).toEqual(
    'Sun Mar 08 2020 08:00:00 GMT-0700 (Pacific Daylight Time)',
  );
  expect(parseISO('2020-03-08 09:00').toString()).toEqual(
    'Sun Mar 08 2020 09:00:00 GMT-0700 (Pacific Daylight Time)',
  );
});