UNPKG

@burglekitt/gmt

Version:

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

github.com/burglekitt/gmt

burglekitt/gmt

30 lines (29 loc) • 2.17 kB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
/** * Return how many distinct UTC calendar dates two UTC intervals share. * * - Counts the number of UTC dates touched by the closed intersection * `[max(aStart, bStart), min(aEnd, bEnd)]` — inclusive of both endpoints. * - Boundaries are UTC boundaries — no DST is involved. * - 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, leap seconds). * - 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 * `intervalIntersectionUtc` with `intervalCountUtc`: * `const span = intervalIntersectionUtc(aStart, aEnd, bStart, bEnd); span ? intervalCountUtc(span.start, span.end, "day") : 0;` * * @param aStart ISO 8601 UTC datetime string for the first interval start * @param aEnd ISO 8601 UTC datetime string for the first interval end * @param bStart ISO 8601 UTC datetime string for the second interval start * @param bEnd ISO 8601 UTC datetime string for the second interval end * @returns number of shared calendar dates, `0` when disjoint, or null on invalid input * * @example intervalOverlappingDaysUtc("2024-01-01T23:59:00Z", "2024-01-02T00:01:00Z", "2024-01-01T23:59:00Z", "2024-01-02T00:01:00Z") // 2 * @example intervalOverlappingDaysUtc("2024-01-01T00:00:00Z", "2024-01-02T00:00:00Z", "2024-01-02T00:00:00Z", "2024-01-03T00:00:00Z") // 1 (adjacent) * @example intervalOverlappingDaysUtc("2024-01-01T00:00:00Z", "2024-01-02T00:00:00Z", "2024-01-03T00:00:00Z", "2024-01-04T00:00:00Z") // 0 (disjoint) * @example intervalOverlappingDaysUtc("invalid", "2024-06-30T23:59:59Z", "2024-04-01T00:00:00Z", "2024-12-31T23:59:59Z") // null */ export declare function intervalOverlappingDaysUtc(aStart: string, aEnd: string, bStart: string, bEnd: string): number | null;