On Mon, 13 Mar 2017 20:11:27 +0000 (UTC), Stijn De Jong wrote:

Date: Mon, 13 Mar 2017 20:11:27 +0000 (UTC)
For example, my date header above should be the generic GMT system date.
(and where my next reply, using the same server, will contain my computer
sysdate.)

By way of example, the date header above will be my system date instead of
GMT (all other things being equal in the two consecutive posts).