I guess someone hard-coded 2010 and beyond as spammy.
See this Slashdot entry for details: http://it.slashdot.org/story/10/01/02/0027207/SpamAssassin-2010-Bug
The "fix" (a punt for a decade really) is to change it to 2020 by changing /usr/share/spamassassin/72_active.cf:
1) search 'FH_DATE_PAST_20XX'
2) change '/20[1-9][0-9]/' to '/20[2-9][0-9]/'
We may wish to make a patch and get it out fast.
SA bug report: https://issues.apache.org/SpamAssassin/show_bug.cgi?id=6269
Another page: https://secure.grepular.com/blog/index.php/2010/01/01/spamassassin-2010-bug/
I set this as "MAJOR" because it adds 3.4 to the spammy scores, which is pretty darn high.
The fix is to sa-update or use 3.2.1-r2 :)
*** This bug has been marked as a duplicate of bug 299256 ***