Incorrect result: 3:00:01 minus 2 second = 1:59:59 depend on env.TZ

[kawanet]

Describe the bug
subtract() method may return an incorrect result with dayjs/plugin/timezone depend on the place where you runs the script.

If you run it at Tokyo, it returns a correct result.
If you run the same code at New York, however, it returns an incorrect value.
Note that we don't have the DST daylight saving time system in Tokyo.
And in the U.S., March 13 was the day to switch from STD to DST at 2022.

const dayjs = require("dayjs");
dayjs.extend(require("dayjs/plugin/utc"));
dayjs.extend(require("dayjs/plugin/timezone"));

const dt = new Date("2022/03/13 03:00:01 -07:00");
const utc = +dt;
const LA = "America/Los_Angeles";
const FMT = "YYYY-MM-DDTHH:mm:ssZ";
let t;

// If you are in Tokyo
process.env.TZ = "Asia/Tokyo";
t = dayjs(dt).tz(LA).subtract(2, "second");
console.log(t.format(FMT), +t - utc);
// => 2022-03-13T02:59:59-07:00 -2000 (not so bad)

// If you are in New York
process.env.TZ = "America/New_York";
t = dayjs(dt).tz(LA).subtract(2, "second");
console.log(t.format(FMT), +t - utc);
// => 2022-03-13T01:59:59-07:00 -3602000 (incorrect)

Expected behavior
subtract() method should return the incorrect result wherever you run the script like moment-timezone have done.

const moment = require("moment");
require("moment-timezone");

// If you are in New York
process.env.TZ = "America/New_York";
t = moment(dt).tz(LA).subtract(2, "second");
console.log(t.format(FMT), +t - utc);
// => 2022-03-13T01:59:59-08:00 -2000 (perfect)

Information

• Day.js Version: 1.11.6
• OS: macOS
• Time zone: America/New_York

[kawanet]

related issue: #2184

[KronosDev-Pro]

Hi 👋

On dev branch, on Day.js v1.11.7 and on #2118 :

describe('issue 2152 - result not match, depends on env.TZ', () => {
  it('Sat Mar 12 2022 09:00:01 NY, LA, TOKYO tz, to NY, LA, TOKYO tz', () => {
    const date = '2022-03-13 03:00:01'
    const LA = 'America/Los_Angeles'

    const mDate = tz => moment(date).tz(tz)
    const dDate = tz => dayjs(date).tz(tz)

    expect(dayjs(dDate(NY)).tz(LA).subtract(2, 's').format()).toBe(moment(mDate(NY)).tz(LA).subtract(2, 's').format())
    expect(dayjs(dDate(NY)).tz(TOKYO).subtract(2, 's').format()).toBe(moment(mDate(NY)).tz(TOKYO).subtract(2, 's').format())

    expect(dayjs(dDate(LA)).tz(NY).subtract(2, 's').format()).toBe(moment(mDate(LA)).tz(NY).subtract(2, 's').format())
    expect(dayjs(dDate(LA)).tz(TOKYO).subtract(2, 's').format()).toBe(moment(mDate(LA)).tz(TOKYO).subtract(2, 's').format())

    expect(dayjs(dDate(TOKYO)).tz(LA).subtract(2, 's').format()).toBe(moment(mDate(TOKYO)).tz(LA).subtract(2, 's').format())
    expect(dayjs(dDate(TOKYO)).tz(NY).subtract(2, 's').format()).toBe(moment(mDate(TOKYO)).tz(NY).subtract(2, 's').format())
  })
}) // pass

Hoping that this will solve your problem 😉

[kawanet]

@KronosDev-Pro
Thank you for giving the test code.
I've just confirmed that the problem is NOT FIXED YET at dev branch commit e70bee7 .

$ TZ=Asia/Tokyo jest test/issues/issue2152.test.js
 PASS  test/issues/issue2152.test.js
  issue 2152 - result not match, depends on env.TZ
    ✓ Sat Mar 12 2022 09:00:01 NY, LA, TOKYO tz, to NY, LA, TOKYO tz (16ms)

$ TZ=America/New_York jest test/issues/issue2152.test.js
 FAIL  test/issues/issue2152.test.js
  issue 2152 - result not match, depends on env.TZ
    ✕ Sat Mar 12 2022 09:00:01 NY, LA, TOKYO tz, to NY, LA, TOKYO tz (17ms)

  ● issue 2152 - result not match, depends on env.TZ › Sat Mar 12 2022 09:00:01 NY, LA, TOKYO tz, to NY, LA, TOKYO tz

    expect(received).toBe(expected) // Object.is equality
    
    Expected value to be:
      "2022-03-12T22:59:59-08:00"
    Received:
      "2022-03-12T22:59:59-07:00"

The problem here is that the day.js's result is not constant but depends on process.env.TZ.

import MockDate from 'mockdate'
import dayjs from '../../src'
import utc from '../../src/plugin/utc'
import timezone from '../../src/plugin/timezone'

dayjs.extend(utc)
dayjs.extend(timezone)

const moment = require("moment")
require("moment-timezone")

beforeEach(() => {
  MockDate.set(new Date())
})

afterEach(() => {
  MockDate.reset()
})

describe('issue 2152 - result not match, depends on env.TZ', () => {
  it('Sat Mar 12 2022 09:00:01 NY, LA, TOKYO tz, to NY, LA, TOKYO tz', () => {
    const date = '2022-03-13 03:00:01'
    const LA = 'America/Los_Angeles'
    const NY = 'America/New_York'
    const TOKYO = 'Asia/Tokyo'

    const mDate = tz => moment(date).tz(tz)
    const dDate = tz => dayjs(date).tz(tz)

    expect(dayjs(dDate(NY)).tz(LA).subtract(2, 's').format()).toBe(moment(mDate(NY)).tz(LA).subtract(2, 's').format())
    expect(dayjs(dDate(NY)).tz(TOKYO).subtract(2, 's').format()).toBe(moment(mDate(NY)).tz(TOKYO).subtract(2, 's').format())

    expect(dayjs(dDate(LA)).tz(NY).subtract(2, 's').format()).toBe(moment(mDate(LA)).tz(NY).subtract(2, 's').format())
    expect(dayjs(dDate(LA)).tz(TOKYO).subtract(2, 's').format()).toBe(moment(mDate(LA)).tz(TOKYO).subtract(2, 's').format())

    expect(dayjs(dDate(TOKYO)).tz(LA).subtract(2, 's').format()).toBe(moment(mDate(TOKYO)).tz(LA).subtract(2, 's').format())
    expect(dayjs(dDate(TOKYO)).tz(NY).subtract(2, 's').format()).toBe(moment(mDate(TOKYO)).tz(NY).subtract(2, 's').format())
  })
}) // pass

[kawanet]

It's not still fixed at commit 231ff0f fix/issue2037 branch as well.