compareYearMonths

Unreleased

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

Signature

compareYearMonths(a: string, b: string): number | null

Compare two year-month strings (YYYY-MM) in calendar order: year first, then month.

• Accepts both year forms, so 2026-10 and +002026-10 compare equal.
• Negative years sort before year 0: -000001-12 is before 0000-01.
• Returns null if either input is invalid or not in the ISO calendar.

Parameters

Parameter	Type	Description
a	string	year-month string
b	string	year-month string

Returns

-1, 0, or 1, or null on invalid input

Examples

import { compareYearMonths } from "@northguild/gmt/plain/compare";

compareYearMonths("2026-09", "2026-10") // -1

a

b

output

 

Source

plain/compare/compareYearMonths.ts