sorting slightly irregular date fields in a pivot table

I have a spreadsheet in Excel 2003 with several thousand rows, and one column contains data like this:

6/25/2009 rev. 7
7/8/2009 rev. 2
7/16/2009 rev. 40

Excel doesn't sort it by date when the data is in a pivot table, putting (for example) 1/5/2009 before 10/15/2008. How can I sort by date in ascending order?