On 2025-10-24 09:55, Dag-Erling Smørgrav via tz wrote:
It means that 00:00:00 on the day DST starts does not exist (the clock goes from 23:59:59 to 01:00:00). This again means that software that uses a datetime with the time set to 00:00:00 to represent a date may conclude that the day DST starts does not exist.
Yes, but that behavior is reasonably common elsewhere, so such software should get fixed anyway. Next year a forward transition at 00:00 is scheduled for March 8 in Cuba, March 29 in the Azores and in Lebanon, April 24 in Egypt, and September 6 in Chile. It's not likely we'll convince all those governments to change their minds merely because some software developers can't get their act together. By staying in sync with most of Chile, the proposed Argentine rule has significant advantages over switching at a time other than midnight. For example, devices that are not updated past tzdb 2025b could set TZ="America/Santiago" next year, and get the correct time according to the proposed Argentine rule.