Pattern

Regex for RFC 2822 date

Email-style date format like RFC 2822.

The pattern

^(Mon|Tue|Wed|Thu|Fri|Sat|Sun), \d{1,2} (Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec) \d{4} \d{2}:\d{2}:\d{2} [+-]\d{4}$

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What it matches

Mon, 12 Jun 2024 10:30:45 +0530
Sun, 1 Jan 2023 00:00:00 -0800

What it doesn't match

12 Jun 2024 10:30:45
2024-06-12T10:30:45Z

Notes & gotchas

RFC 2822 (and RFC 5322) date format used in email headers like Date:, Received:. Mandatory weekday abbreviation and 4-digit timezone offset.

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) or /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. The pattern starts with ^ and ends with $ — it expects the entire input to match. To find this pattern inside a longer text, remove the anchors and use the /g flag for multiple matches.
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 — use RegExp.escape-equivalents in your language.
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.