The date formatting is available through the WordPress admin panel. Go to Settings>General.
You have several default date formatting options:
However in case the default options are not suitable for your needs you are free to create the custom date output.
Select the Custom radio button and in the available filed input your date format.
Here are some examples:
F j, Y – November 6, 2010
l, F jS, Y – Saturday, November 6th, 2010
Y/m/d – 2010/11/06