[tz] attic data for the tz database

[Paul_Koning at Dell.com]

On Aug 29, 2013, at 12:28 PM, Paul Eggert <eggert at cs.ucla.edu> wrote:

> ...
> I like Zefram's suggestion for allowing a multitier
> structure for the tz database.  One way to do that would be
> to add a cutoff year to the Makefile.  It'd default to 1970.
> People who are interested in older timestamps could decrease
> the cutoff to (say) 1900; this would cause links to be
> turned into zones they differ from the existing zones after
> 1900.  Conversely, people who are not interested in (say)
> pre-2000 timestamps could increase the cutoff to 2000, which
> would result in smaller database that turns a zone into a
> link if it's equivalent to another zone after 2000.

That's a useful thing to be able to do.  It's a pretty easy addition to "zic" which I implemented in the version we use internally for the products I work on, exactly for the reason you mention.  So the way to do that isn't so much to partition the source data, but rather to filter which subset of that data is transformed into the output that zic generates.

	paul