ISO 8601 Ordinal Date (YYYY-DDD) Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching iso 8601 ordinal date (yyyy-ddd), ported and verified for JavaScript. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your JavaScript project — whether you're validating in an Express middleware, a Next.js API route, or a client-side form.

Javascript Implementation

// ISO 8601 Ordinal Date (YYYY-DDD)
// ReDoS-safe | RegexVault — Localization > Date Formats

const iso8601OrdinalDateYyyydddRegex = /^((?:19|20)[0-9]{2})-(00[1-9]|0[1-9][0-9]|[12][0-9]{2}|3[0-5][0-9]|36[0-6])$/;

function validateIso8601OrdinalDateYyyyddd(input: string): boolean {
  return iso8601OrdinalDateYyyydddRegex.test(input);
}

// Example
console.log(validateIso8601OrdinalDateYyyyddd("2024-001")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Localization > Date Formats category and carries a ReDoS-safe certification. That matters for JavaScript developers because especially critical in long-running Node.js event loops where a ReDoS vulnerability can block the entire process. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Day 001 = January 1, day 365 = December 31 (non-leap), day 366 is only valid in leap years. Used in DOY-based systems, scientific datasets, and some military applications. Convert to calendar date with date library.