Time with Fractional Seconds and Timezone Regex for Python

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching time with fractional seconds and timezone, 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

# Time with Fractional Seconds and Timezone
# ReDoS-safe | RegexVault — Localization > Time Formats

import re

time_with_fractional_seconds_and_timezone_pattern = re.compile(r'^(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_time_with_fractional_seconds_and_timezone(value: str) -> bool:
    return bool(time_with_fractional_seconds_and_timezone_pattern.fullmatch(value))

# Example
print(validate_time_with_fractional_seconds_and_timezone("12:30:45"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Localization > Time 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=hour, 2=minute, 3=second, 4=fractional, 5=tz sign, 6=tz hour, 7=tz minute. Z = UTC. Fractional seconds up to 9 places (nanoseconds). Half-hour timezones (+05:30 India, +09:30 Australia) are supported.