To me, one of the key framing ideas that almost all dates/times are actually a set of matching-rules that you are monitoring for. You can guess how many seconds

To me, one of the key framing ideas that almost all dates/times are actually a set of matching-rules that you are monitoring for. You can guess how many seconds will elapse until the match triggers, but you can't be totally sure [0] until it happens, and in some cases it will never quite happen at all. [1] Then the second half is often to reverse your "I think it will happen X seconds from now" delta-guess into "I'm also guessing that your timezone's clocks will say Y when it happens." Just don't forget to keep track of which timezones is controlling the event versus which timezones it is being displayed in. ____ [1] Your UTC estimate might occur plus or minus leap seconds. TAI is safer, unless somebody discovers something exciting and new that changes the behavior of cesium atoms. [0] Such as if the time zone vanishes because the country is gone. Or perhaps the 1:30 to 2:00 thing couldn't exactly happen because the clocks went forward from 1:00 to 2:00 with a missing hour.