[tz] zic bug: Wall-clock ordering of transition times

[Paul Eggert]

On 12/31/20 11:22 AM, Brian Park wrote:
> The thing that I was wondering was whether the semantics of the zone info
> text files actually mandated a transition from 2:00 to 1:00 for Grand_Turk,
> if the Zone entry was set to 2:00, instead of its current 3:00 value. Or
> whether the special case in the zic compiler was an additional rule on top
> of the normal semantics of the zone info text files, in order to parse the
> Grand_Turk case properly.

The latter. That is, original semantics would have required two 
transitions there, but when this sort of problem was discovered in the 
mid-1990s the zic behavior was changed by adding the special case. 
Unfortunately, this special case wasn't documented in the zic man page 
until recently.

The recent doc change is here:

https://github.com/eggert/tz/commit/b804a741d5cdb5d1b761de9ad053ba916fa08636

and you can see a recent message about this here:

https://mm.icann.org/pipermail/tz/2020-December/029616.html