title: How can I group by date time column without taking time into consideration
body: <p>I have a bunch of product orders and I'm trying to group by the date and sum the quantity for that date. How can I group by the month/day/year without taking the time part into consideration?</p>
  
  <p><code>3/8/2010 7:42:00</code> should be grouped with <code>3/8/2010 4:15:00</code></p>