[PATCH] libc/time: Add CLOCK_TAI

[Brian Inglis]

On 2025-07-14 09:45, Corinna Vinschen via Newlib wrote:
> On Jul 11 06:35, Sebastian Huber wrote:
>> FreeBSD also provides this clock identifier, maybe it should be
>> #if __BSD_VISIBLE
>> #define CLOCK_TAI		(11)
>> #endif
>> ?

> Probably, but I seriously wonder how to implement CLOCK_TAI on Cygwin.

> IIUC, if you don't do anything special, the CLOCK_REALTIME and CLOCK_TAI
> return the same value, because the leap second is set to 0 at kernel
> startup.  Maybe that's enough...

If you are running an NTP server you just have to ask for the system variable:

$ ntpq -c'rv 0 tai'
tai=37
$ ntpq -c'rv 0 tai,leapsec,expire'
tai=37, leapsec=201701010000, expire=202606280000

assuming you keep it updated from IERS, NIST, and/or USNO upstreams.

Or install tzdata-right to get leapsecond compensated timezones at TAI-10s:

$ ntptime.sh; TZ=right/UTC date +%c%z; date -u +%c%z; TZ=right/$TZ date +%c%z; 
date +%c%z
2025 Jul 14 Mon 20:15:33+0000  JD 2460871.344132  MJD 60870.844132  ToD 72933
NTP 3961512933  Unix 1752524133  TAI-UTC 37  TAI-GPS 19  GPS-UTC 18
GPS We 2375  Cy 2 Wn 327  Wa 71  ToW 159351  DoW 1 ToD 72951
2025 Jul 14 Mon 20:15:06+0000
2025 Jul 14 Mon 20:15:33+0000
2025 Jul 14 Mon 14:15:06-0600
2025 Jul 14 Mon 14:15:33-0600

These are updated with every IERS Bulletin C leapsecond announcement and data 
update, made available in the next tzdata release.

-- 
Take care. Thanks, Brian Inglis              Calgary, Alberta, Canada

La perfection est atteinte                   Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter  not when there is no more to add
mais lorsqu'il n'y a plus rien à retrancher  but when there is no more to cut
                                 -- Antoine de Saint-Exupéry