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

Paul Eggert eggert at cs.ucla.edu
Thu Dec 31 21:14:33 UTC 2020

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:


and you can see a recent message about this here:


More information about the tz mailing list