subtractYearMonth

Unreleased

Not in @northguild/gmt 1.20.0 on npm yet. It is on main and ships in the next release.

Signature

subtractYearMonth(value: string, units: { years?: number; months?: number; }): string

Return a year-month string moved backward by units.

• The same rules as addYearMonth: years and months only ({ days: 1 } and { weeks: 1 } return ""), nothing to clamp, and "" for invalid input.
• The amounts are not negated here, so the sign rules (mixed signs, -0) are Temporal’s.
• The subtraction starts from day 1 of the month, as the specification’s AddDurationToYearMonth does with operation subtract (it negates the duration, then sets [[Day]] to 1), so +275760-09 minus a month is +275760-08 and -271821-05 minus a month is "" (day 1 of -271821-04 is out of range).

Parameters

Parameter	Type	Description
value	string	year-month string

Options

units

the amounts to move the year-month by

Option	Type	Default	Description
years?	number	no years; at least one of years and months must be given.	Whole years to subtract.
months?	number	no months; at least one of years and months must be given.	Whole months to subtract.

Returns

the year-month string after the subtraction, or "" on invalid input

Examples

import { subtractYearMonth } from "@northguild/gmt/plain/calculate";

subtractYearMonth("2026-10", { months: 10 }) // "2025-12"

value

units

output

 

Source

plain/calculate/subtractYearMonth.ts