Accounting Period (YYYY-MM) Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching accounting period (yyyy-mm), ported and verified for JavaScript. Financial data validation has zero tolerance for false negatives — a missed invalid entry can corrupt downstream calculations. 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

// Accounting Period (YYYY-MM)
// ReDoS-safe | RegexVault — Finance > Financial Formats

const accountingPeriodYyyymmRegex = /^((?:19|20)[0-9]{2})-(0[1-9]|1[0-2])$/;

function validateAccountingPeriodYyyymm(input: string): boolean {
  return accountingPeriodYyyymmRegex.test(input);
}

// Example
console.log(validateAccountingPeriodYyyymm("2024-01")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Finance > Financial 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

Capture group 1: year (1900-2099), group 2: month (01-12). Accounting periods usually follow calendar months but some companies use fiscal months not aligned to calendar months.