ISO 8601 Date (YYYY-MM-DD) Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching iso 8601 date (yyyy-mm-dd), 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

# ISO 8601 Date (YYYY-MM-DD)
# ReDoS-safe | RegexVault — Localization > Date Formats

import re

iso_8601_date_yyyymmdd_pattern = re.compile(r'^((?:19|20)[0-9]{2})-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])$')

def validate_iso_8601_date_yyyymmdd(value: str) -> bool:
    return bool(iso_8601_date_yyyymmdd_pattern.fullmatch(value))

# Example
print(validate_iso_8601_date_yyyymmdd("2024-01-15"))  # 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

Capture groups: 1=year, 2=month, 3=day. The pattern does not validate impossible dates like 2023-02-29 (non-leap year) or 2024-04-31 (April has 30 days). Validate calendar correctness with a date library.