Concepts

These pages cover the mental models you need before writing any other GMT code.

• Plain vs Zoned — the two families of Temporal types and why they never mix.
• DST Disambiguation — why wall-clock time breaks twice a year and how GMT controls it.
• Correct at the Edges — the tests that prove GMT is exact at the boundaries a clock can name.
• The Standards — TC39, Temporal, ISO 8601, the RFCs, IANA, BCP 47, CLDR and test262, and what GMT uses each for.