[LEAPSECS] 'right' zone in tzdata on Linux

Henry Hallam henry at pericynthion.org
Mon Jun 22 18:57:31 EDT 2015


Thanks all.  I evidently misunderstood the purpose of the "right"
zones.  My system clock is UTC via NTP from a pool server.  I had
hoped this would be an easy way to find TAI, but it looks like I'll
have to parse the leapsec list.

Cheers, Henry

On Mon, Jun 22, 2015 at 2:32 PM, Steve Allen <sla at ucolick.org> wrote:
> On Mon 2015-06-22T14:03:03 -0700, Henry Hallam hath writ:
>> would return the TAI.  However, it appears to be out by one minute:
>>
>>   $ TZ='right/UTC' date; date -u
>>   Mon Jun 22 21:00:29 UTC 2015
>>   Mon Jun 22 21:00:54 UTC 2015
>
> As of today the value of time_t in a system clock intended to use the
> "right" zones should have a value 25 seconds larger than the value of
> time_t in a system clock intended to use the POSIX zones, just as .
> Warner Losch has also explained.
>
> This is because the "right" clock is presumed to have actually
> counted every second that was broadcast in radio signals, whereas
> the POSIX clock is presumed not to have counted the leap seconds.
> That's the way in which "right" is right, it is the only scheme
> that has counted every second, some rubber, some SI, since
> 1970-01-01, but "right" is not a standard in any other sense.
>
> So when the "right" code translates the time_t to a string
> it subtracts off those 25 seconds before applying the POSIX
> rule for translating time_t to calendar date/time.
>
>> Am I using the 'right' timezone incorrectly, missing something else,
>> or is there an error in the TZ database?
>
> Is your system clock set 25 seconds faster than POSIX wants?
> That's actually kindof hard, because I know of no standard time
> package which will do it.
>
> Pictures of this at
> http://www.ucolick.org/~sla/leapsecs/amsci.html
>
> --
> Steve Allen                 <sla at ucolick.org>               WGS-84 (GPS)
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