Hi on a check out when you choose delivery method it displays a delivery date- The system calculate the delivery date from the delivery time set on courier service.
For example today is 16-06-2015 and if courier service take 1 day delivery then delivery date shows on check out will be for next day 17-06-2015 . Now Only trouble is that it should also have a settings for a cut off time. lets say my cut off time is 1pm and any orders received before 1pm will see delivery date 17-06-2015 but any orders received after 1pm should see delivery date 18-06-2015.
also same way delivery date should not include saturday and sunday.
you can probably make a seperate addons for cut off time and sell it
Kindly let me know if it make any sense