intervalIntersectionDate

Signature

intervalIntersectionDate(aStart: string, aEnd: string, bStart: string, bEnd: string): { start: string; end: string; }

import { intervalIntersectionDate } from "@northguild/gmt/plain/interval";

Return the overlapping span of two date intervals, or null when they do not overlap.

• Uses Temporal.PlainDate.compare for comparison.
• Adjacent intervals (e.g. aEnd === bStart) share one instant and DO overlap.
• Returns null if either interval is invalid (start > end).
• Returns null on invalid input (wrong type, malformed strings).
• Accepts GMT calendar-annotated PlainDate strings — E5 (issue #78). Since the result is a date value, all four arguments must carry the same calendar tag (or all be bare ISO); a mismatch returns null (E5 decision of record D4). The output’s tag is re-derived from the intersection span, never copied from an input.

Parameters

Parameter	Type	Description
aStart	string	ISO 8601 date string for the first interval start, optionally calendar-annotated
aEnd	string	ISO 8601 date string for the first interval end, optionally calendar-annotated
bStart	string	ISO 8601 date string for the second interval start, optionally calendar-annotated
bEnd	string	ISO 8601 date string for the second interval end, optionally calendar-annotated

Returns

{ start, end } with the overlapping span, or null on invalid input / no overlap / mismatched calendars

Examples

intervalIntersectionDate("2024-01-01", "2024-06-30", "2024-04-01", "2024-12-31") // { start: "2024-04-01", end: "2024-06-30" }
intervalIntersectionDate("2024-01-01", "2024-06-30", "2024-06-30", "2024-12-31") // { start: "2024-06-30", end: "2024-06-30" }
intervalIntersectionDate("2024-01-01", "2024-06-30", "2024-07-01", "2024-12-31") // null
intervalIntersectionDate("2024-01-01", "2024-06-30", "2024-02-01", "2024-03-01") // { start: "2024-02-01", end: "2024-03-01" }
intervalIntersectionDate("invalid", "2024-06-30", "2024-04-01", "2024-12-31") // null

Source

plain/interval/intervalIntersectionDate.ts