Pattern

Regex for 24-hour time (HH:MM)

Time in 24-hour format with optional seconds.

The pattern

^([01]\d|2[0-3]):[0-5]\d(:[0-5]\d)?$

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What it matches

00:00
13:45
23:59:59
09:30
12:00:00

What it doesn't match

24:00
12:60
9:30
13:45:60

Notes & gotchas

Hours 00–23, minutes/seconds 00–59. Seconds are optional. For times with fractions, append (\.\d+)?.

Code in your language

Use the explainer's Code tab to generate ready-to-paste snippets in JavaScript, Python, Java, .NET, Go, Ruby, and PHP for this pattern.

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About this pattern

Date and time formats vary enormously across regions and systems. The regex here validates structure only — a date like 2024-02-30 would pass format validation but isn't a real date. After regex passes, parse with your language's date library to confirm semantic validity.

Quick usage in different languages

Once you've validated a candidate value matches this pattern, you'll typically use it inside your application code. Each language has its own regex syntax:

JavaScript: new RegExp(pattern).test(value)
Python: re.match(pattern, value) with raw strings: r"pattern"
Java: Pattern.compile(pattern).matcher(value).matches()
C# / .NET: Regex.IsMatch(value, pattern)
Go: regexp.MustCompile(pattern).MatchString(value) — Go uses RE2 so some advanced features aren't available
Ruby: value =~ /pattern/ or pattern.match?(value)
PHP: preg_match('/pattern/', $value)

The explainer's Code tab generates these for any pattern you paste — including the right escaping and idioms for each language.

Common pitfalls

Anchors matter. If the pattern uses ^ and $ it expects the entire input to match. To find this pattern inside a longer text, remove the anchors and use the /g flag.
Case sensitivity. Letter ranges like [A-Z] only match uppercase. Use the i flag or [A-Za-z] for case-insensitive matching.
Escape user input. If you're building a regex from a string variable, escape regex metacharacters first to avoid bugs or injection.
Performance. For this specific pattern the risk is low, but be cautious of nested quantifiers when adapting it — they can cause exponential backtracking on adversarial input.