[tz] Binary File Format

Paul Eggert eggert at cs.ucla.edu
Thu Sep 10 23:33:38 UTC 2015

Bill Seymour wrote:
> it occurs to me that they might be closed lower bounds instead
> (the corresponding ttinfo is for the period after the transition).

Yes, I think that's right.

> tzfile(5) doesn't say explicitly.

It should.  Proposed patch attached.

> 2.  Basically the same question for the array of leap seconds.

tzfile(5) says it's the leap second count "to be applied after the given time". 
  Seems reasonably clear but I suppose it could be tightened up.  See attached 

> 3. Re the version-'2' array of leap seconds:  each array element
> is a time_t value followed by a count of the number of leap
> seconds after that time.  tzfile(5) says that eight bytes
> are used for each "transition time" and "leap second time";
> but since the count of leap seconds is neither of those,
> is the count still just four bytes?

Yes it is.  Arguably this is a defect, as the total leap second count (assuming 
the current rules) will greatly exceed 2**32 before 64-bit time_t values are 
exhausted.  However, almost surely we'll change our timekeeping practices well 
before that happens, so the defect doesn't really matter much.
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