Denton Liu [off-list ref] writes:
Unfortunately, it seems like mutt wasn't the culprit, it was Gmail
that's been munging the dates. For example, in this patch[1], the date
shows as
Date: Thu, 12 Dec 2019 16:44:50 -0800
even though locally, the output of the format-patch shows as
Date: Mon, 9 Dec 2019 19:25:34 +0100
"git send-email" records the timestamp of sending. If you really
want to force a specific author date, you could add a in-body Date:
but it is discouraged in mailing-list centric workflow, because it
is more natural for everybody other than the author to consider that
the time the patch hits the list, i.e. the public eyes, is when the
patch was "authored".