How can i get difference in base plan and actual/current plan for a project

Hi PS Experts,

How can i get difference in base plan and actual plan .

For example-

Project1 is created for 10 days (start and end date difference).

Now in between -project is extended/changed for 12 days .

What is the way to get 2 days as a difference in base plan and current plan.

Thanks

Suraj prakash