subtractDuration

Signature

subtractDuration(a: string, b: string): string

import { subtractDuration } from "@northguild/gmt/duration/calculate";

Combine two ISO 8601 duration strings by subtraction.

• Uses Temporal.Duration.from and .subtract to combine, then .toString() to re-emit.
• Temporal.Duration.prototype.subtract has no relativeTo option, so combining any pair where either operand has a nonzero years/months/weeks component throws and results in “” — calendar-unit duration arithmetic needs a reference point that this function does not accept.
• The result may be negative (e.g. subtracting a larger duration from a smaller one).
• Returns “” if either operand is not a valid ISO 8601 duration string.

Parameters

Parameter	Type	Description
a	string	ISO 8601 duration string
b	string	ISO 8601 duration string

Returns

ISO 8601 duration string representing a - b, or “” on invalid input

Examples

subtractDuration("P1D", "PT2H") // "PT22H"
subtractDuration("PT1H", "PT2H") // "-PT1H"
subtractDuration("P1Y", "P1M") // "" (calendar units need relativeTo, unsupported)
subtractDuration("P1D", "not a duration") // ""

Source

duration/calculate/subtractDuration.ts