I made a national reservation today for a trip where our arrival and departure times work out to just over 4 24 hour periods. I figured that this would require a 5 day rental and when I put it into the web site it gave me the weekly rate - which is what I assume it always does when you book 5 to 7 days. Here is the strange part, I then modified the arrival and departure times to get inside 4 times 24 hours and the rate for a 4 day rental was more than the rate it gave me for the week. Made it easy for me to book the weekly rate. Is that an anomoly or does it usually work out that way?