[tz] New 'Theory' section "Accuracy of the tz database"

Paul Eggert eggert at cs.ucla.edu
Mon Sep 16 03:51:18 UTC 2013

On 09/15/2013 07:31 AM, Lester Caine wrote:

> I'm seeing 'summertime' transitions prior to 1970. Derick has
> confirmed that he is using the binary data to build the PHP
> libraries, so presumably these are currently included?

Yes, every unique location has a time zone history back to the
introduction of standard time.

> What will the situation be post the 'post-1970 only' clean-up?

No change there.  It's just that there would be fewer unique locations;
more would be like Europe/Vatican, which is simply a link to

>So it would complete the picture if the rare rules like the
>Netherlands could be incorporated while not affecting the base POSIX

We could easily extend the zic input format, without affecting the
output of zic, simply by having it drop fractional seconds.

> It is almost a case that 'extended mode' should support
> fractional seconds anyway?

That hasn't been discussed, but something like that seems reasonable.

> This removes the need to create any new
> timezones for what is essentially outside the scope of the 'default'
> TZ distribution?

I don't think anybody's proposing creating a new zone for every
location on the planet, no.  The problem is that we'd need thousands
of zones merely to handle standard time.

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