[LEAPSECS] Coming of age in the solar system

Zefram zefram at fysh.org
Sun Sep 5 08:03:39 EDT 2010

Ian Batten wrote:

>> The gettimeofday() function shall obtain the current time, expressed

>> as seconds and microseconds since the Epoch, and store it in the

>> timeval structure pointed to by tp. The resolution of the system clock

>> is unspecified.


>A strict reading of that (assuming seconds means SI seconds and "since"

>means elapsed) is probably TAI(now) - TAI(epoch): it's an elapsed


Another part of POSIX explicitly defines "seconds since the epoch"
in a way that doesn't mean seconds since the epoch. It means
a lossily-encoded form of UTC, using the trivial formula that
ascribes 86400 seconds to each day, regardless of actual day length.
It refers to UTC by name, and the rationale explicitly discusses
leap seconds. This was discussed on this list less than a year ago;
see particularly messages <7197.1255273729 at critter.freebsd.dk> (PHK)
and <20091012102721.GK20296 at fysh.org> (me).


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