Excel 2007 Date Factor

I have a spreadsheet of inventory items and the dates are in various formats Europe , USA , and Eastern.
Example below. What I need to do is select all the dates and covert into one recognizable formula
Month (1) Day (1) Year (****). Let me know how to do this. Thanks!

7/12/00
28/12/00

21/12/00
21/12/00

26/12/00
28/12/00

23/01/01
25/01/01

04/01/01
11/01/01

1/2/2001

6/1/2001
27/01/01

8/11/00
27/01/01

select the cells of interest
right click within that selection
select Format Cells... from the context menu
select Custom from the Category: column
select m/d/yyyy from the Type: column
select OK to close and apply the formatting