ISO 8601 Date-Time (Combined, Full) Regex for Python

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching iso 8601 date-time (combined, full), 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-Time (Combined, Full)
# ReDoS-safe | RegexVault — Localization > Date Formats

import re

iso_8601_datetime_combined_full_pattern = re.compile(r'^((?:19|20)[0-9]{2})-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])[T ](2[0-3]|[01][0-9]):([0-5][0-9]):([0-5][0-9])(?:\.(\d{1,9}))?(?:Z|[+-](?:2[0-3]|[01][0-9]):[0-5][0-9])?$')

def validate_iso_8601_datetime_combined_full(value: str) -> bool:
    return bool(iso_8601_datetime_combined_full_pattern.fullmatch(value))

# Example
print(validate_iso_8601_datetime_combined_full("2024-01-15T12:30:45Z"))  # 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

Combines date and time with T or space separator. Fractional seconds up to 9 places. Timezone: Z (UTC) or ±HH:MM. This is the primary format for API timestamps, database storage, and log files. Capture groups: 1=year, 2=month, 3=day, 4=hour, 5=min, 6=sec, 7=fractional.