[time-nuts] Leap seconds and POSIX

[Magnus Danielson]

>> : In practice, in platforms that have access to GPS, NTP is used to
>> : servo the local computer clock into alignment with UTC (or GPS System
>> : Time (UTC without the accumulated leaps) in systems that abhor time
>> : steps), and there is a transient error just after a leap second while
>> : NTP recovers.
>>
>> When the INS bit is set in the NTP packets, NTP tells the kernel about
>> it, which replays the last second of the day to keep in step.  I'm not
>> sure this is a transient error or not, since ntp_gettime can be used
>> to determine that this is the leap second for applications that care.
>> However, it does introduce a glitch in the data produced by system
>> interfaces that don't have leap second indicators...
> 
> Platforms vary because NTP is at the mercy of the kernel developers. 
>  From the standpoint of the average user, there is a transient error. 
> Not that many average users will notice, so long as nothing crashes 
> or hangs.

For many of the places where POSIX is being used these days, this kind 
of reasoning is not helpful to say the least.

For instance, it is being used in many systems where high availability 
as well as propper logging is concerned. In addition to that, UTC may 
very well be the time-scale of choice, thought TAI could be used if 
properly identified as such.

If POSIX standard time where TAI and NTP was steering it as TAI in all 
the boxes, then things would work. We would need to convert into UTC and 
then into local time-zone as part of presentation.

If POSIX standard time where UTC and NTP was steering it as UTC in all 
the boxes, then things would work. We would need to convert into local 
time-zone as part of presentation.

Oh, time-zone is a presentation issue and not a "box" issue.

Cheers,
Magnus