Have a DATETIME column and try to search in af:query advance mode,
Using between operator, open the af:date, put your date and your time and select pm
If you open again this date, the default am is selected. That is the component does not keep your selection of pm
Of course search does not work, because if you put between 10/11/2010 10.45.00 am - 10/11/2010 10.45.00 pm, it will return no results because it will interpret it as between 10/11/2010 10.45.00 am - 10/11/2010 10.45.00 am
Not sure yet if it is a bug. I ll try to have a sample application reproducing it.