I am working on a sheet for my boss due asap. I can't figure out how to get it to calculate though. I have:

Date In -- Date Out -- Date of
01/01/2016 -- 01/03/2016 -- 01/01/2016
01/02/2016 -- 01/03/2016 -- 01/02/2016
01/03/2016 -- 01/03/2016 -- 01/03/2016


I basically want to add a fourth column to show how many items/ persons where at x on the "Date of" so 01/01/2016 should be 1 ... 01/02/2016 should equal 2... and 01/03/2016 should be 3....

I have to do this with a years worth of information. Can someone please help me.