I have worked in storage a long time. I have used 1st of the month (at PS) and did not like that system. Everywhere else, I have been able to use anniversary date for the due date. You can always adjust a date for a customers convenience.

But, other than at PS, I have not prorated in or out. When you rent a storage space, whether from a small company like where I am now, or the 4th largest (USI), we have rented for a month at a time. I have been known to tell my customers that we are like McDonald's. When you buy that Big Mac, even though you may only want to eat 1/2 of it, you bought the whole burger. It never seems to be a problem. (Also, I have a problem picturing turning in a 1/2 eaten Big Mac for a refund or prorate.)

Bob