Date
The HTTP Date header indicates the date and time at which the origin server generated the message.
Usage
The Date header records the exact moment a message was created. Origin servers include this header in every response so downstream caches and clients know when the content was produced. The timestamp feeds into freshness calculations: the Age header value is derived from the difference between the current time and the Date value.
Proxies and CDNs preserve the original Date value
when serving cached responses. Comparing Date to
the local clock reveals how old a cached copy is. The
Cache-Control max-age directive
works together with Date to determine remaining
freshness.
The value follows the IMF-fixdate format:
Date: <day-name>, <day> <month> <year>
<hour>:<minute>:<second> GMT
Values
day-name
The abbreviated day of the week: Mon, Tue, Wed,
Thu, Fri, Sat, or Sun.
day
A two-digit day of the month, zero-padded when
necessary (e.g. 01, 15, 30).
month
A three-letter month abbreviation: Jan, Feb,
Mar, Apr, May, Jun, Jul, Aug, Sep,
Oct, Nov, or Dec.
year
A four-digit year (e.g. 2025).
hour
A two-digit hour in 24-hour format (00 through
23).
minute
A two-digit minute (00 through 59).
second
A two-digit second (00 through 59).
GMT
All dates in this header are expressed in Greenwich Mean Time, which has no offset from Coordinated Universal Time (UTC).
Example
A response generated on a Wednesday at 08:00 UTC. The server created this response at the start of the day, and the timestamp anchors freshness calculations for all downstream caches.
Date: Wed, 01 Jun 2025 08:00:00 GMT
A Last-Modified header often appears alongside Date to show when the underlying resource last changed, while Date shows when the response was assembled.
Date: Fri, 14 Feb 2025 12:30:00 GMT
Last-Modified: Mon, 10 Feb 2025 09:00:00 GMT
Deprecated date formats
Older HTTP implementations used two alternative
formats. These are considered obsolete but some
parsers still accept them for backward
compatibility: Sunday, 06-Nov-94 08:49:37 GMT
(the old date format) and Sun Nov 6 08:49:37 1994
(asctime format).
Takeaway
The Date header records when the origin server generated the message, providing the baseline timestamp for ==Age== calculations and Caching freshness decisions across the delivery chain.
