On 12/08/2017 12:12 PM, Michael Deckers via tz wrote:
Allowing negative AT values would provide a "convenient notation" to avoid the Chatham Rules, as in
Rule NZ 2008 max - Apr Sun>=1 -10:00u 0 S
Good point. I hadn't thought of that. We should make that change in a year or two, after the zic.8 documentation change has had time to percolate.
zic.8 ought to be patched to make explicit that AT and SAVE have no small range limits.
Yes, and it may also be necessary to state the meaning of such extensions; for instance, the suffixes u, g, z currently are allowed for SAVE values but they cannot really be used because it is not clear what they are supposed to mean in this context.
Sorry, I don't see a problem here. The u suffix means "treat the date and time as UTC". If the time is -02:00, that means 22:00 the previous day UTC. I installed the attached patch to zic.8 to try to document the longstanding zic interpretation better.