Garrett Wollman wrote in <25407.23180.512283.959616@khavrinen.csail.mit.edu>: |<<On Thu, 6 Oct 2022 15:35:01 -0700, Guy Harris via tz <tz@iana.org> said: |> On Oct 6, 2022, at 1:41 PM, Brooks Harris via tz <tz@iana.org> wrote: |>> I would add that Posix relies on the c standard, | |> Which appears neither to mandate nor forbid leap seconds. ... |The POSIX standard, on the other hand, requires that time_t be an |integral type, and gives a closed-form formula for how a UTC time is |to be converted to a time_t which explicitly requires every day to be |exactly 86,400 seconds long. (POSIX does not include tzcode's |timegm() interface; applications are expected to copy the formula from |the standard.) The practical upshot of this is that POSIX systems |that implement leap seconds must tick the same second twice for a |positive leap second, and must skip a tick if there is ever a negative |leap second -- either way, making interval calculations inaccurate if But only to throw in that for most systems which are not always-on, and even for some which are, this is rather hypothetic since hardware clocks that i know drift (and Linux hwclock(8) documents "The Hardware Clock is usually not very accurate. However, much of its inaccuracy is completely predictable - it gains or loses the same amount of time every day. This is called systematic drift.") To misuse this drift (it is -2.577933 per ~35 hours here without /etc/adjtime) to adjust clocks seems quite natural; to me being able to keep a human clock (civil time) synchronized with the real day length of our planet remains a cultural achievement, even extending the according predictive capabilities of Stonehenge or the Pyramids (in fact many cultures had something similar it seems). I agree it is all wrong and when i really focus on the problem i am always frustrated how bad i code. CLOCK_TAI would be an alternative for programming purposes, and having a nice leap second table at hand is a good thing (on the according ML PH-Kamp came over with a DNS-based solution for leap announcement a few years back, later stating he was just reiterating an idea from over a decade earlier: i jumped on this idea, because i really liked it!) Unfortunately CLOCK_TAI is not available everywhere. --steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt)