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

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 Go. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your Go project — whether you're validating in a Gin handler, a gRPC service, or a command-line tool.

Go Implementation

// Japanese Date Format (YYYY年MM月DD日)
// ReDoS-safe | RegexVault — Localization > Date Formats

package validation

import "regexp"

var japaneseDateFormatYyyymmddRe = regexp.MustCompile(`^((?:19|20)[0-9]{2})年(0?[1-9]|1[0-2])月(0?[1-9]|[12][0-9]|3[01])日$`)

func ValidateJapaneseDateFormatYyyymmdd(s string) bool {
    return japaneseDateFormatYyyymmddRe.MatchString(s)
}

// Example
// fmt.Println(ValidateJapaneseDateFormatYyyymmdd("2024年1月15日")) // 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 Go developers because Go's RE2 engine is inherently safe from catastrophic backtracking, but this pattern has been additionally verified for correctness. 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.