On 16 Nov 2015, at 21:42, Random832 <random832@fastmail.com> wrote:

Ken Murchison <murch@andrew.cmu.edu> writes:
Having studied up the tzfile(5) format and written some code to
produce these files, I'm wondering why the files in zoneinfo-leaps
include the leap records AND adjust the transition times by the
appropriate number of leap seconds. This seems redundant to me. If
the file includes the leap second records, why not let the consumer
adjust the transitions?

Because the values are meant to be time_t timestamps, and for these
files they're intended for a notional system in whose time_t 946684822
rather than 946684800 represents a date of 2000-01-01 00:00:00 UTC..

Also Posix specifically says that there are 86400 seconds in a day, every day, without exception. It allows for the time 23:59:60 by saying that the time in seconds is /approximately/ the time since midnight at the start of 1970 …

It’s a mess, but it’s a well-intentioned mess. t + 86400 is this time tomorrow. For those few people who are prepared to do arithmetic “properly” (tomorrow might be t + 86399 or t + 86401) the timezone files including leap seconds are available. That’s not a posix system though … you pays your money, you takes your choice.

jch