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

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 PHP. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your PHP project — whether you're validating in a Laravel validator, a WordPress plugin, or a standalone PHP script.

Php Implementation

<?php
// ISO 8601 Date-Time (Combined, Full)
// ReDoS-safe | RegexVault — Localization > Date Formats

define('ISO_8601_DATETIME_COMBINED_FULL_PATTERN', '/^((?: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])?$/');

function validate_iso_8601_datetime_combined_full(string $input): bool {
    return (bool) preg_match(ISO_8601_DATETIME_COMBINED_FULL_PATTERN, $input);
}

// Example
var_dump(validate_iso_8601_datetime_combined_full("2024-01-15T12:30:45Z")); // bool(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 PHP developers because especially relevant in PHP where PCRE backtracking limits can trigger silent failures on malicious input. 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.