Glossary

UTC

The global reference time. Calendar systems store instants in UTC and display them in local timezones.

Coordinated Universal Time is the timezone-neutral reference clock. Well-built calendar systems store each timed event as a UTC instant plus a display timezone, which keeps events unambiguous when viewed from anywhere.

Storing local wall time without a timezone is the classic bug: the event means different instants to different viewers, and daylight saving transitions silently shift it. UTC storage plus timezone-aware display avoids both.