Talk:Unix time/Archives/2020

Age of the Universe has Chagned

Age of the universe has changed. Please update. — Preceding unsigned comment added by 2601:581:C000:CA60:E10A:F3E4:D435:8600 (talk) 19:22, 16 January 2020 (UTC)

Unix time does represent UTC

The last sentence of the 1st paragraph states: "Due to this treatment, Unix time is not a true representation of UTC."

However, the previous statements and examples underneath indicate that Unix time maps directly to UTC: At any midnight, Unix time is always an integer multiple of 86,400 seconds - which UTC reflects. Unix time and UTC are both adjusted during a leap second event, in the same way by effectively "holding" for a second. In that sense, Unix directly represents UTC.

It would be consistent to delete the word "not" from that confusing sentence, and thus state: "Due to this treatment, Unix time is a true representation of UTC."

Thanks.

Tim Atkins — Preceding unsigned comment added by 156.68.237.132 (talk) 23:22, 29 May 2020 (UTC)

UTC represents the last second of 2016-12-31 as 23:59:60, with the previous second being 23:59:59. See, for example, ITU-R Recommendation TF.460-6, section Annex 1, section 2 "Leap-seconds", which says, in paragraph 2.2, "A positive leap-second begins at 23h 59m 60s and ends at 0h 0m 0s of the first day of the following month.", and Annex 3, "Dating of events in the vicinity of a leap-second", which shows an example of an event occurring at "30 June, 23h 59m 60.6s UTC".

No time representation that gives those two seconds the same representation can be a true representation of UTC. Guy Harris (talk) 23:37, 29 May 2020 (UTC)

Guy, thanks for the response. I understand your point here, which is of course valid. When I read the subject sentence I was thinking in context of absolute timescales such as TAI. During the transition you described, Unix time should be considered undefined or invalid; certainly any implementation of Unix time during that transition needs special handling or interpretation. However, apart from these leap-second events, conversion between a UTC representation and its Unix representation is constant; that was my main point. Thanks for clarifying the important exception! — Preceding unsigned comment added by 156.68.234.7 (talk) 22:55, 30 May 2020 (UTC)

Year 275760 problem

In JavaScript, the year that can be entered as a Date object is -271821 to 275760 years, and an error occurs when the year exceeds 275760.--58.236.219.11 (talk) 09:15, 18 October 2020 (UTC)