If you find a data with date column in which date has been stored as shown below
05.06.2010 it is read as June 05, 2010, but it can also be read as May 06, 2010. The correct one is June 05, 2010 according to my regional settings.
If you replace the full stop sign with slash sign,it is possible that the date is converted to May 06,2010 which is incorrect answer.
Now 05/06/2010 is a correct date. The DATE Function convert and make the date according to your regional settings in the computer.