Common mistake that I don't think the author got right either, is that if you want something to happen at a future local time time, say 2PM in São Paulo at some date next year, you don't use UTC + a timezone, you use local time + timezone.
Timezones are not immutable, and timezone database updates happen every year. Only if you track dates that happen in the past UTC makes sense.
In some cases/jurisdictions they change DST quite late so you'll only know with certainty what UTC time corresponds with what local time a few weeks in advance.
Timezones are not immutable, and timezone database updates happen every year. Only if you track dates that happen in the past UTC makes sense.
In some cases/jurisdictions they change DST quite late so you'll only know with certainty what UTC time corresponds with what local time a few weeks in advance.