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Old dates have weird minute offsets in utc

See original GitHub issue

Describe the bug Take this as an example:

// loop same day every 11 years for the past 200 years
for (let i = 2022; i > 1800; i -= 11) {
  console.log(dayjs(`12/31/${i}`).utc(true).toDate());
}

Expected behavior

2022-12-31T00:00:00.000Z
2011-12-31T00:00:00.000Z
2000-12-31T00:00:00.000Z
1989-12-31T00:00:00.000Z
1978-12-31T00:00:00.000Z
1967-12-31T00:00:00.000Z
1956-12-31T00:00:00.000Z
1945-12-31T00:00:00.000Z
1934-12-31T00:00:00.000Z
1923-12-31T00:00:00.000Z
1912-12-31T00:00:00.000Z
1901-12-31T00:00:00.000Z
1890-12-31T00:00:00.000Z
1879-12-31T00:00:00.000Z
1868-12-31T00:00:00.000Z
1857-12-31T00:00:00.000Z
1846-12-31T00:00:00.000Z
1835-12-31T00:00:00.000Z
1824-12-31T00:00:00.000Z
1813-12-31T00:00:00.000Z
1802-12-31T00:00:00.000Z

Actual behavior

2022-12-31T00:00:00.000Z
2011-12-31T00:00:00.000Z
2000-12-31T00:00:00.000Z
1989-12-31T00:00:00.000Z
1978-12-31T00:00:00.000Z
1967-12-31T00:00:00.000Z
1956-12-31T00:00:00.000Z
1945-12-31T00:00:00.000Z
1934-12-31T00:00:00.000Z
1923-12-31T00:00:00.000Z
1912-12-31T00:06:00.000Z   /// what???
1901-12-31T00:06:00.000Z
1890-12-31T00:06:00.000Z
1879-12-31T00:03:44.000Z   /// huh??!
1868-12-31T00:03:44.000Z
1857-12-31T00:03:44.000Z
1846-12-31T00:03:44.000Z
1835-12-31T00:03:44.000Z
1824-12-31T00:03:44.000Z
1813-12-31T00:03:44.000Z
1802-12-31T00:03:44.000Z   /// it goes on like this until 100 AC

Information

Day.js Version ^1.11.4
OS: MacOs Big Sur 11.6
NodeJS
Time zone: [e.g. GMT+03:00 DST]

Issue Analytics

State:
Created a year ago
Comments:14 (5 by maintainers)

Top GitHub Comments

1reaction

BePo65commented, Jul 25, 2022

One of the problems of offset is the handling of seconds (see issue #1905).

1reaction

BePo65commented, Jul 25, 2022

why does .utcOffset(0,true) has another results

Using utcOffset with 1 parameter, sets the utcOffset of a given dayjs object.

Using utcOffset with 2 parameters, sets the utcOffset of a given dayjs object while keeping the time value of that object. And therefore using .utcOffset(0, true) gets other values (this fragment avoids the critical branch in the code).

Regarding that point, the documentation is not really complete (at least I didn’t find it in the documentation, only in the source code). @Bykiev : perhaps you want to make a PR for the documentation on the corresponding project?

Back to time zones / utcOffset:
sorry that it took me so long to understand the issue. If I get it right, your point is not about correct definition of timezones. The point is that .utcOffset(true) does not keep the local time. And that is really an error in dayjs.

I’m working on a pr for this issue; give me a few days.