[tz] Fwd: Bulletin C number 57

Brian Inglis Brian.Inglis at SystematicSw.ab.ca
Fri Feb 1 15:20:06 UTC 2019

On 2019-02-01 05:43, Tony Finch wrote:
> Paul Eggert wrote:
>> One cannot simply translate the IERS file to the NIST file, as the NIST file
>> has information that the IERS file lacks, namely, the last time that the data
>> were changed.
> Isn't that always 5ish months before the last leap second? :-)

Normally within 10 (exceptionally 15) workdays after six months before the
previous leap second.

For NIST source, this should be same as the numeric suffix of the real name of
the file symlinked from leap-seconds.list and the internal update timestamp,
which are only updated when a new leap second is announced in Bulletin C and
inserted into the file.
After every Bulletin C which does not announce a leap second, only the expiry
timestamp and file modified date are updated some time later.

For IERS and USNO sources, this is updated by Bulletin C every six months, so
the real name numeric suffix and the internal update timestamp reflect that.
File real name numeric suffix and the internal update timestamp used to be
rounded to the UTC day but the IERS now sets those to arbitrary actual times.

All expiry timestamps are set to the 28th of the month before the possible
following leap second in the next Bulletin C announcement (allowing for future
possible quarterly or monthly leaps).

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

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