Compare two dates

Compare validated ISO calendar dates in UTC and return -1, 0 or 1.

JavaScript Version 1.0.0 · MIT · .md

function compareDates({ first, second }) { return Math.sign(new Date(first).getTime() - new Date(second).getTime()); }

Try in the local lab Download function

Input & expected output

Input

{
  "first": "2026-10-28",
  "second": "2026-10-29"
}

Expected output

-1

The edge case

Input

{
  "first": "2024-02-29",
  "second": "2024-02-29"
}

Expected output

Know the limits

The lab requires real YYYY-MM-DD calendar dates and validates before execution.
This compares UTC calendar dates, not local business days or ambiguous date strings.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Source & maintenance

Curated implementation; explicit input bounds, edge cases, local fixtures and rebuilt presentation. Original MDX retained as inert source evidence.

Maintained by Oveyon. Original source commit: 14b481cf60df. This edition’s file: contents/compare-two-dates.mdx in akamind/1loc, commit 0a77f131b22d. Read the license.

Local fixture scope · Node.js 22.23.2 · reviewed October 28, 2026. No external service is required.

Keep exploring

Add AM PM suffix to an hour — Turn an hour from 0 to 23 into a 12-hour label with am or pm.
Calculate the number of days between two dates — Count whole calendar days between two YYYY-MM-DD dates.
Convert a date to YYYY-MM-DD format — Format an ISO date-time as its UTC calendar date.