Time with Fractional Seconds and Timezone Regex for JavaScript

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 JavaScript. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your JavaScript project — whether you're validating in an Express middleware, a Next.js API route, or a client-side form.

Javascript Implementation

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

const timeWithFractionalSecondsAndTimezoneRegex = /^(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]))?$/;

function validateTimeWithFractionalSecondsAndTimezone(input: string): boolean {
  return timeWithFractionalSecondsAndTimezoneRegex.test(input);
}

// Example
console.log(validateTimeWithFractionalSecondsAndTimezone("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 JavaScript developers because especially critical in long-running Node.js event loops where a ReDoS vulnerability can block the entire process. 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.