OQL group by dateTime problem

Hi All, I have a form with some data that users submit and  I want to count the number of forms submitted per day in a barChart. My OQL query looks something like this: 'SELECT COUNT(*) as NumberOfForms, FormDate  FROM MainModule.myform GROUP BY FormDate' But because the FormDate is a DateTIME field the count is always 1.  (because the time is always different for multiple forms on the same day)  So how can I do a GROUP BY on Date but not dateTime?? I prefer not to add another datetime to my entity. Anybody with a smart idea on how to solve this??