checking out by date

Hi All,

I have a very large repository that imported into git from CVS with about 5 years worth of history.

Today I decided to checkout some code from the past:

$ git checkout master@{"Mon Dec 31 2007"} warning: Log for 'master' only goes back to Tue, 2 Dec 2008 16:57:15 -0800.

Then proceeds to checkout a code snapshot from 2 Dec. To work around this I checked out a specific commit id, by looking at the log:

commit 3771ec1d6ccf329da378b7633fdef60474eac4b7
Author: XXXXXXXXXXXXXXX
Date:   Mon Dec 31 23:25:17 2007 +0000

    BugId: none
    correct wrong commit

$ git checkout 3771ec1d6ccf329da378b7633fdef60474eac4b7 ... HEAD is now at 3771ec1... BugId: none correct wrong commit

So what has caused git to be unable to process the date information, even though the information is clearly in the history ? Did I miss something ?

Dave