<!DOCTYPE html><html><head><title></title><style type="text/css">p.MsoNormal,p.MsoNoSpacing{margin:0}
p.MsoNormal,p.MsoNoSpacing{margin:0}</style></head><body><div>I am curious to hear that your TZDB parsing is exposed to your end-users and is in the critical path. I would have thought that the parsing would be done offline (e.g. after each TZDB release), and the TZDB data would be converted into a different format that is more amenable to the computation that your code is performing.<br></div><div><br></div><div>With regards to the data format of the TZDB, I have not seen great problems with the parsing. It's the *interpretation* of that data which is incredibly difficult and tricky. I'm not sure that using different format, like JSON, would help with the interpretation part.<br></div><div><br></div><div>With regards to 25:00, I believe that should be interpreted as: "This transition occurs at exact 25 hours after the beginning of the first Saturday on or after the 8th of September". The implicit 'w' for "wall time" is not a real physical clock on the wall, but a hypothetical clock keeping time in the local time zone just before the transition.<br></div><div><br></div><div><br></div><div>On Tue, Apr 4, 2023, at 12:24, Jacob Pratt wrote:<br></div><blockquote type="cite" id="qt" style=""><div dir="auto"><div>That is definitely what I intend to do for where it's necessary, but the code path will almost certainly be slower, which is a significant factor to consider in my situation (it's a widely used library).<br></div><div dir="auto"><br></div><div dir="auto">Ultimately it would be great if there were a generated file in a common format (such as JSON) so that everyone doesn't have to write their own parser. But that's a separate issue.<br></div><div dir="auto"><br></div><div dir="auto"><div>With regard to Japan, did the clock read 24:59:59 before going to 0:00? I'm not sure how else to interpret 25:00.<br></div><div><br></div><div class="qt-gmail_quote" dir="auto"><div dir="ltr" class="qt-gmail_attr">On Tue, Apr 4, 2023, 10:53 Brian Park <<a href="mailto:brian@xparks.net">brian@xparks.net</a>> wrote:<br></div><blockquote class="qt-gmail_quote" style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0.8ex;border-left-color:rgb(204, 204, 204);border-left-style:solid;border-left-width:1px;padding-left:1ex;"><div><u></u><br></div><div><div>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.<br></div><div><br></div><div>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.<br></div><div><br></div><div>On Tue, Apr 4, 2023, at 02:49, Jacob Pratt via tz wrote:<br></div><blockquote type="cite" id="qt-m_-1842395477796048927qt"><div dir="ltr"><div>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).<br></div><div><br></div><div>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.<br></div><div><div><div dir="ltr"><div dir="ltr"><div><div dir="ltr"><div><br></div><div>Jacob Pratt<br></div></div></div></div></div></div></div></div></blockquote><div><br></div></div></blockquote></div></div></div></blockquote><div><br></div></body></html>