Glossary · Phase 0 · Tools
UTC
Coordinated Universal Time: the world's reference clock, with no daylight saving. Programs store times in UTC and convert for display.
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A date has no time; a datetime is one moment; a timedelta is a length of time, with no start date.
Learn it properly
Dates, times and time zones · datetime, timedelta, formats, time zones and the traps when clocks change. About 40 minutes.
Other terms from the same lesson
- ISO 8601: The standard way to write dates and times as text, like 2025-03-14T09:12:00, which sorts correctly and can't be misread.
- time zone: A region's clock rules: its offset from UTC and when its clocks change, named like America/Denver.
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