intervalLengthDateTime

Signature

intervalLengthDateTime(start: string, end: string, unit: string): number

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

Return the exact length of a datetime interval in unit, as a real (possibly fractional) number.

• Distinct from intervalCountDateTime, which counts calendar/clock unit boundaries crossed rather than measuring exact duration — an interval from 23:59 to 00:01 touches 2 day boundaries via intervalCountDateTime but has an exact length of ~0.0014 days via intervalLengthDateTime.
• Uses Temporal.Duration.prototype.total, which resolves calendar units (month, year) against the interval’s own start so a partial month is expressed as a true fraction rather than truncated.
• Returns 0 for a zero-length interval (start === end).
• Returns null on invalid input (unparseable start/end, start > end, unsupported unit).

Parameters

Parameter	Type	Description
start	string	ISO PlainDateTime string for the interval start
end	string	ISO PlainDateTime string for the interval end
unit	string	unit string — any DateTimeUnit

Returns

exact length of the interval expressed in unit, or null on invalid input

Examples

intervalLengthDateTime("2024-01-01T23:59:00", "2024-01-02T00:01:00", "day") // 0.001388888888888889
intervalLengthDateTime("2024-01-01T23:59:00", "2024-01-02T00:01:00", "minute") // 2
intervalLengthDateTime("2024-01-01T00:00:00", "2024-01-01T00:00:00", "day") // 0
intervalLengthDateTime("invalid", "2024-01-02T00:00:00", "day") // null

Source

plain/interval/intervalLengthDateTime.ts