See this page for a demonstration of the issue:
http://discoursedb.org/wiki/Date_querying_test
The comparison part of the query ("[[Was published on::>2008-01-01]]") gets ignored; pages with all dates are displayed.
Version: unspecified
Severity: normal
There was a glitch in the recent updates to the Date type. The problems are fixed now in SVN, but pages with dates that have been created/modified in the meantime may need to be stored again to fix the DB entries. Using the repair mechanism on Special:SMWAdmin would also work if many pages are affected.