How do I change a cells value from this

3/04/2012 5:21:20 p.m.

To this

3/04/2012

Basically erasing any time value off the end

I'm trying to create a pivot table, even if I format cells to the date format (so it just displays 3/04/2012) it still contains the time value within the cell and treats each date as an individual value in the pivot table.

Any help would be appreciated