Date

This HTTP response header indicates the date and time when the response was generated by the server. It will look something like this: Date: Wed, 01 Jan 2023 07:30:00 GMT and should be in the following format:

This header can be used by caches to determine the age of the document. Caches need to know the age in order to know whether to serve the cached version of the resource, or to fetch the document again from the server. The cache needs to know what time the server thinks it is in order to correctly determine the age of the document. This is because the server's clock could be incorrect or could have drifted significantly from the cache's value. The Expires Header is used to determine when documents should expire from the cache.