I have noticed messages every once and a while which cause mutt to
mis-interpret the date.  I have produced one below which shows up in
the mutt index with a date of "Apr 15".  (mutt-1.0pre3us-1)  Save this into
~/muttbug and then run "mutt -f ~/muttbug" to open it as a folder.  I made
this out of a real folder/message, stripping out email addresses and excess
headers.

From test@test  Thu Mar  9 10:37:59 2000
Date: Thu, 9 Mar 00 10:52:56 EST
Message-Id: <0000@test>
From: "test" <test>
To: me
Subject: test mutt date
Sender: test
Reply-To: test@test
Status: RO

Stupid test message