Accounting Period (YYYY-MM) Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching accounting period (yyyy-mm), ported and verified for Python. 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 Python project — whether you're validating in a Django view, a FastAPI endpoint, or a standalone data processing script.

Python Implementation

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

import re

accounting_period_yyyymm_pattern = re.compile(r'^((?:19|20)[0-9]{2})-(0[1-9]|1[0-2])$')

def validate_accounting_period_yyyymm(value: str) -> bool:
    return bool(accounting_period_yyyymm_pattern.fullmatch(value))

# Example
print(validate_accounting_period_yyyymm("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 Python developers because particularly important in Python web servers where CPU-bound regex operations can stall concurrent request handling. 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.