dayjs("2021-01-26T14:25:04.871Z", "YYYY-MM-DDTHH:mm:ss.SSSZ") doesn't work

[beckyconning]

Describe the bug
dayjs("2021-01-26T14:25:04.871Z", "YYYY-MM-DDTHH:mm:ss.SSSZ") doesn't work
moment("2021-01-26T14:25:04.871Z", "YYYY-MM-DDTHH:mm:ss.SSSZ") works

Expected behavior
Should work as moment does treating Z as +00:00

Information

• Day.js Version 1.10.3
• OS: Node v10.16.3
• Browser: Node v10.16.3
• Time zone: London

[iamkun]

fixed in #1359

[ghiscoding]

@beckyconning
Have you tried this code change in strict mode?

Since this is not released yet so I tried to manually modify the customParseFormat.js minified file with your code change and in strict mode it seems to fail the isValid check.

const format = 'YYYY-MM-DDTHH:mm:ss.SSSZ';
const inputDate = '1993-12-01T10:22:33.128Z';
const isDateValid = dayjs(inputDate, format, true).isValid(); // returns false

I use this Zulu format a lot in my open source lib and this is the only piece missing to migrate to DayJS

so I then cloned the project and tried adding this unit test in customParseFormat.test.js and it indeed fails

describe('Strict mode', () => {
  // ...

  it('zulu', () => {
    const input = '2021-01-26T15:38:43.000Z'
    const format = 'YYYY-MM-DDTHH:mm:ss.SSSZ'
    expect(dayjs(input, format).isValid()).toBe(true)         // ok
    expect(dayjs(input, format, true).isValid()).toBe(true)  // fails
  })
})

I traced the problem up to the date !== this.format(format) and that is where it fails because the date is not equal to the format result, so I think the format() function has to replace the Z by -00:00 or something like that? I'm not sure what to do to fix this

these lines 227-229

// in my case date is '2021-01-26T15:38:43.000Z' 
// and this.format() is '2021-01-26T10:38:43.000-05:00' 
// so they are not strictly equal and it fails

      if (isStrict && date !== this.format(format)) {
        this.$d = new Date('')
      }

[tbastyns]

@ghiscoding

When I escape the 'Z' as such 'YYYY-MM-DDTHH:mm:ss.SSS[Z]', I get the expected results when I use strict mode:

  expect(dayjs('2022-01-21T12:12:12.123Z', 'YYYY-MM-DDTHH:mm:ss.SSS[Z]').isValid()).toBeTruthy();
  expect(dayjs('2022-01-21T12:12:12.123Z', 'YYYY-MM-DDTHH:mm:ss.SSS[Z]', true).isValid()).toBeTruthy();
  // set month to 13; should not be accepted in strict mode
  expect(dayjs('2022-13-21T12:12:12.123Z', 'YYYY-MM-DDTHH:mm:ss.SSS[Z]').isValid()).toBeTruthy();
  expect(dayjs('2022-13-21T12:12:12.123Z', 'YYYY-MM-DDTHH:mm:ss.SSS[Z]', true).isValid()).toBeFalsy();

(don't forget to extend customParseFormat!)

[ghiscoding]

oh ok I didn't know we had to escape it [Z], thanks for the clarification, will test it later.
BTW, your last 2 lines have the same date input (month 13), I think you meant month 12 for the truthy one

[tbastyns]

the last 2 lines illustrate one of the differences of strict VS non-strict: only when using strict, a 13th month is considered invalid