isValidDateInterval

Signature

isValidDateInterval(start: string, end: string): boolean

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

Return true if start and end form a valid date interval — both parseable as

• ISO PlainDate strings and start <= end.
• Both inputs must be ISO 8601 date strings (e.g. "2024-01-01").
• Equal start === end is valid.
• Invalid input, malformed strings, or leap-second strings return false.
• Accepts GMT calendar-annotated PlainDate strings — E5 (issue #78). Ordering is calendar-independent, so start/end may carry different or no calendar tags (D4).

Parameters

Parameter	Type	Description
start	string	ISO 8601 date string (interval start), optionally calendar-annotated
end	string	ISO 8601 date string (interval end), optionally calendar-annotated

Returns

true if start and end form a valid date interval, or false on invalid input

Examples

isValidDateInterval("2024-01-01", "2024-12-31") // true
isValidDateInterval("2024-01-01", "2024-01-01") // true
isValidDateInterval("2024-12-31", "2024-01-01") // false
isValidDateInterval("invalid", "2024-12-31") // false
isValidDateInterval("5785-01-01[u-ca=hebrew]", "2024-12-31") // true (mixed calendars — ordering is calendar-independent)

Source

plain/interval/validate/isValidDateInterval.ts