I don't think I made myself clear... According to the documentation, the Rule says that the time change ran ends on the Sunday before the 15th for the years 1978, 1979, and 1980. The documentation should indicate what you say is true: Rule Macau 1978 1980 - Oct Sun>=15 0:00 0 - I read the line above as follows: In October 1980, the rule changed to standard time. So at this point, refer to the Zone. The Zone says: 8:00 Macau MO%sT 1999 Dec 20 # return to China Meaning use the Macau rules until Dec 20, 1999 There are no Macau Rules after October of 1980. SO... in my mind it means we revert to the overall rule of the Zone for that period. The Zone says it is in effect from 1912 through 1999 - use Macau rules. If there are no rules, then revert back to the rule of the Zone. That makes you correct in that the Zone is 8:00 offset from GMT not 7:34:20 LMT. What doesn't make sense if why a set of Rules is used that ends prior to the end of the period used by the zone. It's a moot point but it confuses the flow. Perhaps a "max" in place of the 1980 would make this more clear. It would not interrupt the flow because the Zone says ignore Macau after 1999. The max is used elsewhere. Why is it NOT used here? ________________________________________ From: kre@munnari.OZ.AU [kre@munnari.OZ.AU] Sent: Tuesday, February 22, 2011 8:00 AM To: tz@lecserver.nci.nih.gov Subject: Re: Macau Date: Tue, 22 Feb 2011 11:14:18 +0000 From: jrl <jrl@terraatlas.com> Message-ID: <E468A544C5BEF74DBF22CAAB3FD50DE810F47BBB@UNIVERZ.terraatlas.local> | What is the correct rule for Macau from 1980 through 1999? | Did they return to LMT? I wonder if there is any way we can make the documentation clearer that the rules do not specify intervals, but transition points. People keep asking questions (like this one) that make no sense at all if the rules are interpreted correctly, but would be perfectly legitimate if the rules were doing something like "specifying the period when summer time applies". Since this mistake is so commonly made, it must be a problem with the tz documentation. Unfortunately, I can't see it (which is often true when someone who knows the answer tries to see why others cannot see it). Does anyone have any ideas how we can make this clearer? Is the problem that people are just reading the data files, and ignoring the documentation? Do we need to add some explanatory comments in every data file? kre ps: the Macau rules say that the last time there was a std/summer time transition in Macau was the 3rd SUn in October, 1980, since then the only change has been the change of time zone abbreviation when Macau became part of China again. So, no, it dod not revert to LMT, there simply were no more transitions - and once you understand that the rules are used to specify transition points, this is really all very obvious.