I'm looking at nopcommerce as a possible Hotel Room booking solution.
I can see that the Rental facility allows for items to be rented for a certain number of days. But I can't see how to have the end date automatically inserted.
I played briefly with that, and it looks like it would require custom programming. The question might be does it matter? If you want rental by the week, then set it that way. If someone does three days, they still pay for the week. If they do 8 days they pay for two! If I get time ( I don't get much of that) I will try to look more tomorrow or the next day.