[time-nuts] Leap Quirks

[Magnus Danielson]

Chuck Harris skrev:
> One of us is confused about what time_t is... I think it is
> you.

I know of three different ways to interpret it. They fit different purposes.

> time_t is a 32 bit (depreciated), or 64 bit integer that contains
> the number of seconds since the epoch.  It is not to be adjusted
> for leap seconds according to POSIX, and unix convention.

This is one, no two, of the interpretations I know of.

> Everything to do with UTC and leap seconds is a library function
> in most unixes that translates the leap second free time_t into
> the leap second adjusted UTC.

Exactly where? Do please tell me what the unified way of getting UTC 
time is. Oh, when there is a leap second it needs to give correct 
counting as well.

Joe has in private conversations pointed out a POSIX interface which 
could be used.

> Again, are you telling me that time_t is getting adjusted for leap
> seconds?  If so, when did this change?

To the best of _my_ knowledge (which can be wrong) this is what is being 
done in practice, which is outside of the POSIX standard, but has the 
effect that 00:00:00 always midnight, which POSIX needs. This is a third 
interpretation...

If somebody (say PHK) got out and slapped my face and say this is a 
total misunderstanding, this is pretty good after all. If this practice 
does exist, then we still have three interpretations and they are in 
conflict with each other even after giving up on introducing leap 
seconds. So we have two or three interpretation of the POSIX timescale, 
one with pure SI seconds, one with rubber seconds up till 
1972-00-00T00:00:00Z and then SI seconds and a third which is like the 
second but re-aligned on each leap second event so that midnights match.

This is only an issue if the POSIX scale is under external control.

And yes, do tell me how I get UTC on all platforms.

Regardless, this just shows how complex the issue is. There seems that 
there is no "correct" interpretation that everyone can agree with as a 
basis. If there is I'll be much happier and go away a bit wiser.

Cheers,
Magnus