[tz] TZif version 4 (was: zoneinfo generating issues)

Derick Rethans derick at derickrethans.nl
Wed Mar 17 18:36:49 UTC 2021

On Tue, 16 Mar 2021, Paul Eggert via tz wrote:

> On 3/12/21 9:58 AM, Paul Eggert wrote:
> > On 3/12/21 1:55 AM, Ian Abbott wrote:
> > > 
> > > For (B), would adding an extra leap-second record at the expiry time with
> > > no difference in correction value work? That would not conform to RFC
> > > 8536, but seems unlikely to break any thing unless that thing is strictly
> > > checking that correction values differ by exactly 1.
> > 
> > Exactly my thought. Unfortunately tzcode itself is picky here (because I
> > mistakenly made it picky when helping to write RFC 8536). I doubt whether
> > anyone else is so picky unless they're imitating tzcode itself. That being
> > said, we'll need to be a bit cautious here, and not introduce this change
> > willy-nilly.
> After thinking about it a bit I installed the following patches to implement
> the above suggestions:
> https://mm.icann.org/pipermail/tz/2021-March/029934.html
> https://mm.icann.org/pipermail/tz/2021-March/029940.html
> Since the affected TZif files do not conform to Internet RFC 8536 it appears
> we'll need a new TZif version number, version 4, to mark files with this new
> feature. This new version number will appear only on the problematic files
> that are generated with leapsecond data that contains an explicit "Expires"
> line, and such data will not be generated by default.

How would I be able to generate such a TZif4 file, so that I can test 
whether timelib can read them correctly? FWIW, timelib doesn't support 
leapseconds for calculations, but I do need to know whether I can read 
the files.


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