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

[Paul Eggert]

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
Europe/Rome.

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

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.