intervalIntersectionDate

Signature

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

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

• Uses Temporal.PlainDate.compare for comparison.
• Half-open: an interval holds every t with start <= t < end. The intersection is [max(aStart, bStart), min(aEnd, bEnd)) when aStart < bEnd && bStart < aEnd (CORE-6’s intersectIntervals), otherwise null.
• Touching intervals (aEnd === bStart) share no day and return null.
• An empty interval (start === end) intersects only an interval it lies strictly inside, and then returns itself.
• Returns null if either interval is invalid (start > end).
• Returns null on invalid input (wrong type, malformed strings).
• Accepts RFC 9557 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

Members

Member	Type	Description
start	string	The date the interval begins on, as an ISO 8601 date (YYYY-MM-DD). It keeps a calendar annotation such as [u-ca=hebrew] when the inputs carry one.
end	string	The first date after the interval, in the same format as start. It is exclusive: the interval holds everything from start up to but not including this value. It can equal start, which makes the interval empty.

Examples

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

intervalIntersectionDate("2024-01-01", "2024-06-30", "2024-04-01", "2024-12-31") // { start: "2024-04-01", end: "2024-06-30" }

aStartaEndbStartbEnd

output

 

Source

plain/interval/intervalIntersectionDate.ts