I've posted a patch that I believe fixes this last-date problem (described here:
http://sdm.openacs.org/sdm/one-baf.tcl?baf_id=1886). The patch is here:
http://sdm.openacs.org/sdm/one-patch.tcl?patch_id=507.
I'm not sure how the release on the patch page ended up getting listed as 4.2. The patch was created against the current 4.6 branch in cvs.