[tz] New Yorker article on David Mills and NTP

[John Haxby]

> On 3 Oct 2022, at 20:58, Steve Allen via tz <tz at iana.org> wrote:
> 
> On Mon 2022-10-03T15:45:59-0400 Garrett Wollman via tz hath writ:
>> And of course both communities end up having to paper over the mistake
>> that the POSIX committee made with regard to leap seconds, but do it
>> in different, not entirely compatible ways.
> 
> The POSIX committee did not make a mistake about leap seconds.
> They had no choice.
> Doing anything else would have required the existence of an authority
> who had already created a robust scheme for communicating the list of
> past and future leap seconds.  No such authority was ever funded, and
> that was because the leap second itself resulted from earlier
> instances of failure to communicate.


I think the problem goes back further than that.

Back in the early 70s there were 86400 seconds in a day, every day.  It was only with the advent of leap seconds that some days has 86401 or 86499 seconds.  The trouble is, programs get to this time tomorrow by adding 86400 to the current time: that constant is implicit (or explicit) in so many places fixing that would have been well-nigh impossible and add significant complexity to even the most mundane shell script.

So Posix says "there are 86400 seconds in a day"[1] and the epoch, time zero, isn't exactly the dawn of the 1970s[2].   The enormously simplifies all time calculations at some minor cost of annoying astronomers :) and making elapsed time and time-of-day different: sleep(86400) isn't sleep until this time tomorrow and using gettimeofday() to measure elapsed time sometimes returns a negative number[3].

jch

[1] https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html, section 4.16
[2] not even in the UK because we stayed on BST that winter.
[3] this did cause some programs to crash, spectacularly.


> 
> --
> Steve Allen                    <sla at ucolick.org>              WGS-84 (GPS)
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