Create a View in your database to return the AM/PM value. Then you can search that field as part of your View.
If you can't do views because of your MYSQL version, you can probably do it in the recordset directly... either way the syntax will be something like:
SELECT *, DATE_FORMAT(yourDateColumn,'%p') AS AMPMValue FROM yourTable
Then you should be able to search based on the AMPMValue column as if it were a text column in your database.