Thunderbird header 'date' display -

[Bob Goodwin]

Until changing to F-9 Thunderbird used to display the e-mail sender's 
time and offset in the header above the text field like "14:03:08 -0500" 
instead of "15:03" which is an almost totally useless bit of information 
[to me] and is already displayed in the list of incoming messages.

I've spent a lot of time looking for the reason but to no avail.  Any 
idea why and how to restore it?

Bob