[tz] Leap Second Support Interval Field Request - RFC8536

[Paul Eggert]

On 12/5/19 9:09 PM, Arthur David Olson wrote:

> Zone    Etc/Leapendstat 0       -       PRE     2020 Jun 28
>                          0       -       POST

Although that would let someone determine leap second validity by 
examining a different file (or issuing another TZDIST request), Michael 
Veth was asking for a way to determine leap second validity by examining 
the same TZif file that contains the leap-second records.

On 12/6/19 3:48 AM, Michael H Deckers wrote:

>    Why not produce a tzdb Zone for TAI? As if we had
> 
>        Zone    Etc/TAI  0:00:10 -      TAI     1972 Jul  1
>                         0:00:11 -      TAI     1973 Jan  1
>                         ....
>                         0:00:35 -      TAI     2015 Jul  1
>                         0:00:36 -      TAI     2017 Jan  1
>                         0:00:37 -      TAI     2020 Jun 28
>                         0:00:37 -      N_A 

This won't have the desired effect. For example, it would cause the 
Etc/TAI clock's adjacent ticks to be 1972-06-30 23:59:59 and 1972-07-01 
00:00:01, whereas the adjacent ticks should be 1972-06-30 23:59:60 and 
1972-07-01 00:00:00. Also, when compiling the Etc/TAI zone with -L 
leapseconds, the resulting TZif file would have incorrect transitions 
because each leap second would be applied twice.