getDstTransitions

Signature

getDstTransitions(timeZone: string, year: number): DstTransition[]

import { getDstTransitions } from "@northguild/gmt/zoned/get";

List every DST transition instant for an IANA timezone within a given year.

• A “transition” is any UTC offset change: a spring-forward gap (nonexistent local time) or a fall-back overlap (ambiguous local time) — see docs/dst-disambiguation.md for the gap/overlap terminology. This is distinct from hasDaylightSaving (whether a zone observes DST at all) and from the disambiguation/offset options (what to do when constructing a single instant that lands in a gap/overlap).
• Most zones have 0 or 2 transitions per year; some (e.g. Africa/Casablanca, which pauses DST for Ramadan) can have more.
• Returns [] for an invalid timeZone, a non-integer year, or a valid zone with zero transitions in that year (not an error case).

Parameters

Parameter	Type	Description
timeZone	string	IANA timeZone identifier
year	number	calendar year to scan (must be an integer)

Returns

array of { instant, offsetBefore, offsetAfter }, in chronological order

Related types

• DstTransition

Examples

getDstTransitions("America/New_York", 2024)
// [
//   { instant: "2024-03-10T07:00:00Z", offsetBefore: "-05:00", offsetAfter: "-04:00" },
//   { instant: "2024-11-03T06:00:00Z", offsetBefore: "-04:00", offsetAfter: "-05:00" },
// ]
getDstTransitions("Asia/Tokyo", 2024) // []
getDstTransitions("Invalid/Zone", 2024) // []

Source

zoned/get/getDstTransitions.ts