pypi / tzdata
tzdata
What changed in tzdata 2026, from its official release notes, upgrade guides and advisories. Sources checked 2026-10-19.
1 breaking5 behavior and defaults7 fixes and other
See which of these apply to your code, ranked, in your agent:
npx @unstale/cli inittzdata 202613 changes
Breaking changes 1
Alberta is modeled as permanently -06 using CST, with the change temporarily occurring on 2026-11-01 at 02:00.
Behavior and default changes 5
Manitoba is modeled with permanent -05 and the abbreviation EST from 2026-11-01 at 02:00.
The backward compatibility link now uses the abbreviation EST for affected timestamps.
Northwest Territories time will stay at -06 year-round, using the abbreviation CST; the change is modeled from 2026-11-01 at 02:00.
Morocco moves to permanent UTC without daylight saving time transitions on 2026-09-20 at 02:00.
Western Sahara is affected by Morocco's move to permanent UTC without daylight saving time transitions on 2026-09-20 at 02:00.
Fixes and other changes 7
The historical fallback in Ireland is corrected to 1925-09-20.
Corrects Colombia’s 1992 spring-forward time to 00:00 instead of 24:00.
Corrects Iran’s 1979 spring-forward time to 00:00 instead of 24:00.
The backward-compatibility name now conforms better to POSIX, using US federal rules rather than rules of places like New York for timestamps before 1966-10-30 at 01:00 standard time.
The backward-compatibility name now conforms better to POSIX, using EST and EDT abbreviations and US federal rules for timestamps before 1966-10-30 at 01:00 standard time.
The backward-compatibility name now conforms better to POSIX, using US federal rules rather than rules of places like New York for timestamps before 1966-10-30 at 01:00 standard time.
The backward-compatibility name now conforms better to POSIX, using US federal rules rather than rules of places like New York for timestamps before 1966-10-30 at 01:00 standard time.