[image] `DateTime` arithmetic on `Microsecond` (or smaller) scale Specifically, the documentation states that Dates assumes Universal Time - Wikipedia , which is basically solar time, meaning that the lengths of days and seconds are nonuniform due to variations in the earth’s rotation. This is co…

[image] barrettp: Are you sure you mean UT/UT1 and not UTC Yes, UT/UT1 and not UTC, as mentioned a couple of times in the documentation and elaborated on in a footnote: Dates · The Julia Language [image] barrettp: Does that mean that DateTime converts UTC to UT1? No, I don’t think so.…

[image] `DateTime` arithmetic on `Microsecond` (or smaller) scale module now needs to know about leap seconds (assuming UTC timestamps). https://docs.julialang.org/en/v1/stdlib/Dates/#footnote-1 Footnote notes that in the time model used for DateTime there are no leap seconds. (Edit: LOL, jus…

It would appear that the decision has already been made to end leapseconds. [image] `DateTime` arithmetic on `Microsecond` (or smaller) scale Internals & Design @Oscar_Smith brought up an argument for why it shouldn’t error - namely, imagine using DateTime and its arith…

[image] dlakelan: if the time model used in the generation of the data has leap seconds then yeah, you’ve got issues, provided that a leap second occurred within the bounds of your dataset The obvious issue is that calculated intervals may be off by a second (so much for nanosecond precision)…

The documentation is incorrect. Timestamps are generated by clocks, i.e. hardware. In Julia the now() function asks the OS what time it is, and the OS reads the hardware clock. Other software has comparable functionality to generate time stamps via the OS from a clock, and these timestamps might al…

There are two separate questions here: Is now() actually, meaningfully UTC in a way that breaks this UT1 assumption? Implementation-wise, it grabs its value from Libc’s count of seconds since the POSIX epoch — and that does not include leap seconds in its count, explicitly assuming that there are…

Good questions. Is now() actually, meaningfully UTC? With NTP (normally automatically configured and up and running, you never worry about it or touch it) and standard internet connections now() is UTC (plus TZ offset) accurately to a few tens of msec. If there is a nearby accurate NTP server, …

UT1 is not what you think it is. It is a timescale based on the diurnal motion of the stars, actually distant radio galaxies. It is measured twice per day. It is therefore not equal to 86400 seconds per day, because the Earth’s rotation and the motion of the Earth around the Sun varies by millisecon…

I think I may understand: your objections are not so much that we ignore leap seconds or that we use a non-SI-length second; it’s that we (ab)use the term UT1 to describe such assumptions?

Yes, the documentation, and discussion, should not refer to UT1. For someone like me with some knowledge of time standards this is confusing. It would be good to precisely define what, if any, time standard is being used so as not to mislead potential users.

Universal Time vs UTC Time in Dates

General Usage

mihalybaci August 25, 2023, 3:54pm 7

It would appear that the decision has already been made to end leapseconds.

Topic		Replies	Views
Higher resolution DateTime/TimeStamp Internals & Design dates	44	10736	February 13, 2019
Is Dates.UTInstant UT1, UT2, or UTC? General Usage question	4	1241	June 29, 2018
`DateTime` arithmetic on `Microsecond` (or smaller) scale Internals & Design dates , datetime	99	4619	August 26, 2023
[ANN] UTCDates.jl Package Announcements	1	333	May 15, 2026
Discussion about DateTime from POSIX timestamp. Was (incorrect assumption): Dates in Windows - error in datetime from posix Performance package , dates	9	463	March 16, 2024

Universal Time vs UTC Time in Dates

Related topics