[LEAPSECS] internet drafts about zoneinfo

[Tony Finch]

On Sun, 6 Mar 2011, Joe Gwinn wrote:

>

> So, we have an instant in time that is forever fixed,


Yes.


> and a progress rule that counts out uniform seconds (ideally SI seconds

> the standard says in the Rationale).


No. POSIX time does not define a progress rule. It is defined by a formula
that maps UTC time labels into a flat counter.


> The actual requirement is "As represented in seconds since the Epoch,

> each and every day shall be accounted for by exactly 86400 seconds."


That is a rephrasing of part of the defining formula. The preceding
sentence is "How any changes to the value of seconds since the Epoch
are made to align to a desired relationship with the current actual
time is implementation-defined." What the two together mean is that the
counter goes up by 86400 per day regardless of any adjustments to align
the clock with "actual time" (whatever that means).


> > What has been said many times is that it might be nice to change POSIX time

> > to be based on TAI but if you try it you find that this breaks most

> > timekeeping code.

>

> Why?


Because the code assumes that the formula in section 4.15 gives the
relationship between UTC and posix time.

Tony.
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