i have a start_date in format mm/dd/yyyy , then i create attributes called N_O_D and end_date
example ::
start_date N_O_D end_date
11/20/2016 3 11/22/2016
if i key in 4 in N_O_D , then the end_date becomes 11/23/2016
if i key in 12 , end_date becomes 12/01/2016
how to do the calculation on date ?