Thanks everyone for the kind words.
To verify the OP's question, yes, if checking in on the 18th you would call on this 19th to reserve the 1st day. Think of it as if you were making a single day's reservation where you would truly be checking out on the 19th. Or you can think of it as another way: You want five nights, the 18th thru 22nd, checking out on the 23rd. You already know if you make the entire reservation at one time, you would call this 23rd, Right?
Well, for your five nights vacation making the reservation day-by-day, (temporarily ignoring the existance of weekends when MS is closed), you would make five calls, which would be the 19th, 20th, 21st, 22nd, 23rd. Again, your last call is on the 23rd just as it would have been had you not called day-by-day.
As Granny said, be sure to let them know on the first call that you are doing a day-by-day reservation. This tells them ahead of time that when you call next all they have to do is reserve the next day and link it to the previous day(s) already reserved. No need to get further information about your traveling party, etc.
Anyone else interested in downloading the planner, just follow the link in the signature below.
Bill