Analytics, average number of calls during a period (not just a day)

I need to know our busiest hours during a specific period (e.g., the past two months). Currently, you have this report by day; however, our volume of calls varies. Also, it should show the cumulative in each hour, so I can know what percentage of our calls in that period happens in a specific hour or hour. For example, in the last trimester 57% of our calls happened between 11 am and 2 pm.