for simulating the supply chain changed delivery process, I need to create the plan-delivery date and quantity and new-requested delivery date and quantity by inputing the differnce of the plan-delivery date/quantity and new-requesed delivery date/quantity, e.g:
plan-delivery date : 01, Mar,2016 -> datetime format
new-delivery date: 5, Mar. 2016 -> datetime format
the difference delivery date is: 5, Mar. 2016 - 01, Mar,2016 = 4 days -> real format
But plan-delivery date is attributed by datetime format , when the difference is attributed by real formate. So is there anyone here to tell me how to program the manuplication of datetime reffering to the changed delivery date ?