RFC 2822 Date Format for Email and HTTP

RFC 2822 — Email and HTTP Date Format

RFC 2822 (and its predecessor RFC 822) defines the date format used in Internet email headers, HTTP protocol headers, and RSS/Atom feeds. While less popular than ISO 8601 for new APIs, it remains critical for email and web infrastructure.

Format Structure

Sat, 28 Feb 2026 14:30:00 +0900

Breaking this down:

• Sat — Three-letter weekday abbreviation (optional)
• 28 — Day of month (1 or 2 digits)
• Feb — Three-letter English month abbreviation
• 2026 — Four-digit year
• 14:30:00 — Time in 24-hour format
• +0900 — Timezone offset (no colon separator)

Key Differences from ISO 8601

Feature	ISO 8601	RFC 2822
Month	Numeric (02)	English abbreviation (Feb)
Separator	T	Space
Timezone	+09:00 or Z	+0900 or abbreviation
Weekday	Not included	Optional prefix
Sortable	Yes (string sort works)	No (requires parsing)

Timezone Abbreviations

RFC 2822 allows named timezone abbreviations:

• UT / GMT — Universal/Greenwich Mean Time (+0000)
• EST / EDT — Eastern Standard/Daylight Time (-0500/-0400)
• CST / CDT — Central Standard/Daylight Time (-0600/-0500)
• MST / MDT — Mountain Standard/Daylight Time (-0700/-0600)
• PST / PDT — Pacific Standard/Daylight Time (-0800/-0700)

However, numeric offsets are strongly preferred because timezone abbreviations are ambiguous (CST can be Central Standard Time, China Standard Time, or Cuba Standard Time).

Language Patterns

Language	Pattern
JavaScript (date-fns)	EEE, dd MMM yyyy HH:mm:ss xx
Python	%a, %d %b %Y %H:%M:%S %z
Java	EEE, dd MMM yyyy HH:mm:ss XX
PHP	D, d M Y H:i:s O
Go	Mon, 02 Jan 2006 15:04:05 -0700