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

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 PHP. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your PHP project — whether you're validating in a Laravel validator, a WordPress plugin, or a standalone PHP script.

Php Implementation

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

define('ISO_8601_ORDINAL_DATE_YYYYDDD_PATTERN', '/^((?: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 validate_iso_8601_ordinal_date_yyyyddd(string $input): bool {
    return (bool) preg_match(ISO_8601_ORDINAL_DATE_YYYYDDD_PATTERN, $input);
}

// Example
var_dump(validate_iso_8601_ordinal_date_yyyyddd("2024-001")); // bool(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 PHP developers because especially relevant in PHP where PCRE backtracking limits can trigger silent failures on malicious input. 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.