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@burglekitt/gmt

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Temporal-based date and time utilities with timezone support and polyfill integration

github.com/burglekitt/gmt

burglekitt/gmt

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/** * Return how many distinct calendar dates two date intervals share. * * - Counts the number of dates touched by the closed intersection * `[max(aStart, bStart), min(aEnd, bEnd)]` — inclusive of both endpoints. * - Adjacent intervals (e.g. `aEnd === bStart`) share one date and count as `1`. * - Returns `0` when the intervals do not overlap at all (a well-defined answer, not * invalid input). * - Returns `null` if either interval is invalid (`start > end`). * - Returns `null` on invalid input (wrong type, malformed strings). * - Diverges from date-fns's `getOverlappingDaysInIntervals`, which rounds up elapsed * 24-hour periods instead of counting calendar dates (its own doc example — Jan 10-20 vs * Jan 17-21 — returns 3 there, 4 here). To reproduce date-fns's number, compose * `intervalIntersectionDate` with `intervalCountDate`: * `const span = intervalIntersectionDate(aStart, aEnd, bStart, bEnd); span ? intervalCountDate(span.start, span.end, "day") : 0;` * * - Accepts GMT calendar-annotated PlainDate strings — E5 (issue #78). A day is a day in every * supported calendar, so this returns the same count whether or not the endpoints are * calendar-tagged, and arguments may carry different or no tags (D4). * * @param aStart ISO 8601 date string for the first interval start, optionally calendar-annotated * @param aEnd ISO 8601 date string for the first interval end, optionally calendar-annotated * @param bStart ISO 8601 date string for the second interval start, optionally calendar-annotated * @param bEnd ISO 8601 date string for the second interval end, optionally calendar-annotated * @returns number of shared calendar dates, `0` when disjoint, or null on invalid input * * @example intervalOverlappingDaysDate("2024-01-01", "2024-06-30", "2024-04-01", "2024-12-31") // 91 * @example intervalOverlappingDaysDate("2024-01-01", "2024-12-31", "2024-02-01", "2024-02-29") // 29 * @example intervalOverlappingDaysDate("2024-01-01", "2024-06-30", "2024-06-30", "2024-12-31") // 1 (adjacent) * @example intervalOverlappingDaysDate("2024-01-01", "2024-06-30", "2024-07-01", "2024-12-31") // 0 (disjoint) * @example intervalOverlappingDaysDate("invalid", "2024-06-30", "2024-04-01", "2024-12-31") // null */ export declare function intervalOverlappingDaysDate(aStart: string, aEnd: string, bStart: string, bEnd: string): number | null;