leapSecond

const leapSecond: RegExp = /^(?:[^[]*?[Tt ]|[Tt]?)\d{2}:?\d{2}:?60(?:[.,]\d+)?(?:[-+Zz[]|$)/;

RegExp fragment matching an ISO 8601 leap second (second 60) in the time of day of a date-time or time string, in every spelling Temporal’s PlainDateTime.from/PlainTime.from grammar parses.

Examples

import { leapSecond } from "@northguild/gmt";

leapSecond.test("2024-12-31T23:59:60Z") // true
leapSecond.test("2024-12-31T23:59:60.123+00:00") // true
leapSecond.test("2024-12-31t23:59:60+00:00[UTC]") // true (lowercase t)
leapSecond.test("20241231 235960Z") // true (space separator, basic format)
leapSecond.test("2024-12-31T23:59:60") // true (no designator: PlainDateTime clamps it)
leapSecond.test("23:59:60") // true (a time: PlainTime clamps it)
leapSecond.test("2024-12-31T23:59:59Z") // false (second = 59)
leapSecond.test("2024-01-01T00:00:00Z[x=T123460Z]") // false (inside an annotation value)

Source

regex/leap-second.ts