US Date Format (MM/DD/YYYY) Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching us date format (mm/dd/yyyy), ported and verified for Python. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. 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

# US Date Format (MM/DD/YYYY)
# ReDoS-safe | RegexVault — Localization > Date Formats

import re

us_date_format_mmddyyyy_pattern = re.compile(r'^(0?[1-9]|1[0-2])/(0?[1-9]|[12][0-9]|3[01])/((?:19|20)[0-9]{2})$')

def validate_us_date_format_mmddyyyy(value: str) -> bool:
    return bool(us_date_format_mmddyyyy_pattern.fullmatch(value))

# Example
print(validate_us_date_format_mmddyyyy("01/15/2024"))  # 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 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

US format is ambiguous outside the US — 01/05/2024 is January 5th to Americans and May 1st to most of the world. Capture groups: 1=month, 2=day, 3=year. Normalize to ISO 8601 for storage.