Count unique number of days

Hi! I'm having a problem creating a formula.

I have data which includes the date of activation for a product and the # of days they had it for.
e.x.
John Smith ~ March 1st ~ 4 days
Jane Smith ~ March 2nd ~ 3 days

I need to know how to count how many people had the product on each day (March 1,2,3,4...)

John Smith needs to be counted on March 1st, 2nd, 3rd, 4th. While Jane should be counted on March 2nd, 3rd, 4th.

Any ideas on how to flush the data from # of days into actual dates? After I do that I should be a simple count function.