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Expires: and Cache-control: max-age=NNN (1) Origin servers may send either or both of Expires: and Cache-control: max-age=N on responses

(2) If both are sent, an HTTP/1.1 implementation SHOULD
obey the Cache-control: max-age=N directive, and so SHOULD ignore
the Expires field value.

(2b) but HTTP/1.0 implementations will ignore it, so servers
SHOULD NOT depend on a cache obeying that directive.

The behavior of max-age in a response should be equivalent to
what would occur if this response had an Expires: field
specifying the same number of seconds since its Date: field,
but max-age overrides an explicit Expires: value.

Not agreed: When neither the Expires: header nor Cache-control: max-age is sent, should the rules determining what assumptions a cache can make about the expiration date depend on whether the origin server is HTTP/1.0 or HTTP/1.1?