Japanese Date Format (YYYY年MM月DD日) Regex for PHP

What this pattern does

This page provides a well-structured, multi-part regular expression for matching japanese date format (yyyy年mm月dd日), 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
// Japanese Date Format (YYYY年MM月DD日)
// ReDoS-safe | RegexVault — Localization > Date Formats

define('JAPANESE_DATE_FORMAT_YYYYMMDD_PATTERN', '/^((?:19|20)[0-9]{2})年(0?[1-9]|1[0-2])月(0?[1-9]|[12][0-9]|3[01])日$/');

function validate_japanese_date_format_yyyymmdd(string $input): bool {
    return (bool) preg_match(JAPANESE_DATE_FORMAT_YYYYMMDD_PATTERN, $input);
}

// Example
var_dump(validate_japanese_date_format_yyyymmdd("2024年1月15日")); // 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

Capture groups: 1=year (western/Gregorian), 2=month, 3=day. Japan also uses its imperial era system (Reiwa/令和, Heiwa/平成, etc.) — those require separate patterns as they reset year numbering.