[tz] Proposed reversions, for moving forward

Paul Eggert eggert at cs.ucla.edu
Fri Aug 8 23:51:53 UTC 2014

Tim Parenti wrote:
> If you assert that the rest of the changes are also better for similar reasons

No, that's too strong.  I assert only that the rest of the changes are 
so small that they won't cause significant problems in practice with 
real-world time stamps from the era.  This is based not only our 
experience with doing these tz changes in the past (we've done 'em, 
multiple times, for many years, with no problems reported); it's based 
also on my experience with the few applications that could conceivably 
use this old data (mostly astrology, but also earthquake records and the 
like), and on my reading of contemporaneous sources.  Timekeeping simply 
wasn't that accurate back then.  The changes in question alter 
timestamps by a few minutes in areas where timekeeping was so sloppy 
that people at the time wouldn't have noticed or cared about the change.

This attitude toward timekeeping still persists in some parts of the 
world.  Last month I talked to someone who recently lived in smaller 
cities of Ethiopia.  Many residents have reasonably high-precision time 
available on their cell phones.  They ignore it, and use Ethiopian time 
-- some use Arab time, which is equally imprecise -- so that meetings 
are scheduled to a precision of an hour or three, maybe, if you're 
lucky.  This is the normal state of affairs for most of the timestamps 
under discussion, except that people back then didn't even have cell 
phones to ignore.

This is why I have no qualms about the experimental post-2014f Russia 
  They're small changes to old time stamps, and they're not going to 
break practical applications, even if they happen to impose Bolshevik 
timestamps on White Army areas, which some probably do.

> there is no such thing as "removing" data from an end user's perspective

This objection would have merit if end users cared about this data to 
1-second precision.  But they don't.  And they're right to not care.

> Perhaps frustratingly, the first task would be to restore the zone data
> (and associated commentary) removed in 2013e and 2014f to this new area.

I already did that, privately, a few weeks ago.  This shouldn't be 
limited to data removed in the last year or two -- it should contain all 
dubious data ever removed, going back to the 1990s.  (I've done that too.)

> the simplest approach would be to add a Makefile target
> which compiles the standard files as usual, then compiles the dubious data
> with a separate call to zic.

Yes, I've done that too, and I'd be fine with that.

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