How to create custom date display format in drupal 7?
If you are comfortable with coding then go for template file changes.
You have to do changes in node.tpl.php.

Else you can do also without coding refer https://stackoverflow.com/questions/8375674/how-can-a-custom-drupal-date-format-be-added

If you have created view for event display then it is easy to display date field as you want.
Go to date fields setting. There is a option for formatter. Like below screenshot. Here you can add custom date display format.