Many stores require mandatory delivery date, they also want delivery date to be validated ,on their operating hours time like order placed after 4pm cannot be delivered on the same day.
This vqmod based extension does the same.It facilitate user to bar special days like Christmas etc and set operating hours so that delivery date could not be made after operating hours.
It makes selecting delivery date mandatory. It lets you set server offset so that any discrepancy between your server and your operating hours is ruled out.
It is ocmod based no core files have been touched or changed
Selected date is visible on order details page which you can sort also and filter also.
you can exclude x dates from today.

Extension is made by shambhal networks who holds the highest opencart reviews on freelancer.com.
More queries you can ask for the extension to shambhalnetworks@gmail.com
Please note that it works with opencart default checkout system and default theme , other custom checkout extensions like onecheckout, quickcheckout etc won't be compatible with this.
To make that compatible extra may be charged but it is not the responsibility of developer to make it compatible with your custom checkout extension.

Compatible with journal2 theme quickcheckout
Compatible with journal3 theme quickcheckout

Just test the extension at
Admin link
slottest/slot123456 as username password
for frontend
Frontend
demo@gmail.com/123456 as demo customer credentials