No.
> b) is the date in GMT?
Don't care.
IMHO The date stamp that is sent back should be the exact string that was
in the "Last-modified" field when the document was first received
by the cache. If the string is different in any way then the server
should assume that the receiving cache has the wrong document and re-serve it.
The receiving cache should not attempt to understand the
semantics of the "Last-modified" date. It should be treated as a
tag provided by the server that the server can match against when it
is sent back in the "If-Modified-Since" field.
Since only the original server makes any semantic interpretation of
the string, it doesn't matter if the timestamp is GMT, or local.
John Ellson
AT&T Bell Labs