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

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 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

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

package validation

import "regexp"

var iso8601OrdinalDateYyyydddRe = regexp.MustCompile(`^((?: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])$`)

func ValidateIso8601OrdinalDateYyyyddd(s string) bool {
    return iso8601OrdinalDateYyyydddRe.MatchString(s)
}

// Example
// fmt.Println(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 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

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.