> Perhaps I’m missing something? Yes, you’re missing something - geography. “Local time” doesn’t include a frame of reference. If you want to have a meaningf

> Perhaps I’m missing something? Yes, you’re missing something - geography. “Local time” doesn’t include a frame of reference. If you want to have a meaningful representation of local time you need syntax to specify where, probably Lat/Long. Then, periodically, the computer can look up the lat/long to see what the rules are there for time, and compare vs the target time. But even THAT doesn’t solve the problem, because you probably don’t want the computer in a tight loop of looking up location rules for time and checking time. But if you do it periodically then there is a nonzero chance that you will miss the event because the rules changed since the last check and the current check happened after the event. And you can’t just use the city names for time zones (e.g. “Europe/London”) because only a very small number of places have such names, and because they really refer to a combination of time zone and DST rules, not to a city, they just choose representative cities. Finally, ISO 8601 does support durations, which RFC 3339 does not, so ISO seems more useful in that regard, but durations are not relative to any epoch.