(Um resumo, em português, deste post está na minha página principal)

It’s that time of the year again when the Brazilian government decides, by decree, when and where Daylight Savings Time begins. Last year Mac OS X users in Brazil had serious problems with that, as Mac OS X 10.2 (Jaguar) had the wrong dates inside the Unix tables that most of the system uses, and another (different!) wrong date inside a legacy table embedded into one of the frameworks, which was used by the Finder and some other applications.

In 2002 I published a patch to fix the Unix tables but couldn’t change the framework table. In addition, some – though not all – users reported a problem with their system snapping back to normal time on New Year’s eve. So this year, I’m waiting until someone else publishes the correction…

At this time, I haven’t got a system running Jaguar in order to test what will happen this year. The legacy table was finally removed in Mac OS 10.3 (Panther), so at least it will act consistently for all system calls and applications. However, it seems that Panther is considering DST as starting on Oct. 12 instead of the decreed date of Oct. 19.

Mac OS 9 users will have no problems, as there is a convenient double checkbox in the Date & Time Control Panel to allow the user to set DST manually. I’ve filed an enhancement request with Apple to put a similar checkbox into Mac OS X, but there’s little or no hope of this being done anytime soon (if ever).

The problem in Brazil is even more complicated, as DST is observed only by certain states in a manner not consistent with the timezones used when DST is not in effect. Additionally, the government may decide to extend or abbreviate the DST period at any time. So a manual checkbox would certainly be the easiest way around the problem.

…or perhaps a GUI viewer/editor for the timezone files… if only I had the time…