I'm a bit confused here. Are you talking about messages you have just received or ones you have had for awhile?
Netscape's default behavior is to show only the time if the date of the message matches the date of your system. Once your system rolls over to a new date, Netscape should start showing both date and time for the message since it is no longer the same date. At least that is how Netscape has behaved for me since I can remember.
I was born by God's dear grace in extraordinary place
Where the Stars and Stripes and the Eagle flies.