Time Zones Are Harder Than They Look

Time zones look simple until you actually have to compute with them. Most people assume every zone is offset from UTC by a whole number of hours. It isn't.

The Offsets Nobody Expects

India runs at UTC+5:30. Nepal runs at UTC+5:45. Some zones observe Daylight Saving Time and shift twice a year; others, like ours here in Harare (UTC+2, year-round, no DST), never move at all.

A naive time zone converter treats every zone as a fixed offset and gets this wrong constantly — silently, which is worse than getting it wrong loudly. A meeting time that's off by 45 minutes because a converter assumed a round-hour offset doesn't throw an error. It just makes someone late, or makes someone miss a call, and they usually don't find out why until afterward.

Retiring What Didn't Hold

Building this properly meant treating each time zone as its own real, sometimes-irregular data source, not a simple math formula. It also meant retiring an earlier custom date/time component that kept failing in ways that were hard to predict — race conditions in the seconds field, state quietly leaking between fields that were supposed to be independent. After the third rebuild attempt didn't hold, we made the call to stop patching a clever-but-fragile component and replace it with something boring on purpose: six plain dropdowns for month, day, year, hours, minutes, seconds, with correct leap-year handling and a 12/24-hour toggle built in from the start.

Boring Was the Right Call

Boring, in this case, was the right call. A time zone converter's entire job is to be quietly, invisibly correct. Nobody notices a good one. Everyone notices a bad one, usually at the worst possible moment.