[tz] [PATCH 2/4] Move obsolescent Americas entries to 'backward'.

Marc Lehmann schmorp at schmorp.de
Wed Aug 28 17:21:44 UTC 2013

On Wed, Aug 28, 2013 at 08:25:35AM -0700, Paul Eggert <eggert at cs.ucla.edu> wrote:
> Sure, but that's always been outside the scope of the tz project.
> As the Theory file notes:
>   the database is not designed for and does not suffice for
>   applications requiring accurate handling of all past times everywhere,
>   as it would take far too much effort and guesswork to record all
>   details of pre-1970 civil timekeeping.

The interpretation I always gave this, and that was consistent with the
"old style maintainance regime", is that pre-1970s data is not guaranteed
to be correct, useful, or complete, but it is occasionally maintained at
best effort base. This can be witnessed by the many pre-1970 changes to
the data over the years.

I think the part you quoted contradicts your recent actions - the fact
that the data isn't provided everywhere implies that data is provided
somewhere, and overall, this part of the Theory file gives no reason to
actively remove pre-1970 data.

The pre-1970 cut-off, IMHO, was always meant as the date from where the tz
database really cares and really tries to get right, while earlier tz data
might be completely wrong, and definitely much less certain.

What makes the tz database so great is its stability. It should be quite
obvious from the reactions on this list that people feel that stability
is threatened, and I thank you for taking it into account by resurrecting
the data. And, as always, thank you for your good work, even if it is
occasionally criticised :)

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