[tz] Changing 24:00 to 0:00 where possible

Brian Park brian at xparks.net
Tue Apr 4 14:53:11 UTC 2023

I wrote my own TZDB parser as well, and my early versions ran into these problems. The solution was to implement an internal version of the "date/time" class/type that could handle 24:00 without complaining. Your code will have to handle Japan's bizarre 25:00 rule for 1948-1951 anyway (Rule  Japan 1948  1951  - Sep Sat>=8  25:00 0 S). Once it handles 25:00, it should be able to handle the 24:00.

I don't speak for the TZDB maintainers, but my impression is that these 24:00 correspond directly to how the regulations and laws are written. That probably makes it easier for human beings to maintain them.

On Tue, Apr 4, 2023, at 02:49, Jacob Pratt via tz wrote:
> While writing a parser for tzdb files, I noticed that some rules are for a given date at 24:00, rather than the following day at 0:00. While in some cases this is unavoidable (Egypt), in others there is no reason this is necessary (Belize).
> I think it would be reasonable to change 24:00 to 0:00 where possible, incrementing the day, day of week, and month as appropriate. This would reduce the need for special casing values to those that have a technical reason.
> Jacob Pratt
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