How to show Days in Case in Drupal Views?
Got it!

In Drupal added the Unix Timestamp format:
Administration/Regional and Language/Formats/Add Format.
For the string I put in U.
Added the Date Type Unix Timestamp

In the View:
Added the Start and End Date fields.
Under Date Format selected the Unix Timestamp type I just created.
Added a Math Expression field with the expression (([end_date]-[start_date])/86400) since there are 86400 seconds in a day.