When Thunderbird shows date/time of a message in mailing list† it uses the `Date` header:
From: Sender <email@domain>
To: mailing list <address>
Message-ID: <...>
Date: *this is what Thunderbird is showing*
AquaMail uses another header (`Received` I believe) and, therefore, it shows another time (several minutes ahead). Did you do that because the `Date` header may depend on the originating mail client?
† I figured time difference out in a mailing list; the topic actually does not relate to mailing lists at all.