I'm not sure that this applies to what the OP was asking, but here is the way that the Harbor Ridge Resort calendar can be different. HR has about 1/2 the units checking in on Saturday and the other 1/2 on Sunday. As long as the new year starts from Monday to Saturday, everyone checking in will be checking in for the same week, for instance week 1. But if the new year starts on the Sunday, that week will be the first week for the Sunday owners; however, the Saturday owners won't be checking in until the 7th of January for their week 1 while during the same weekend the Sunday owners will be checking in on the 8th of January for the start of their week 2. For the entire year, each weekend will be a checkin for different weeks. So what HR does, is change the calendar so that for week 1 checkins for Saturday would be January 7 and week 1 checkins for Sunday would be January 8. Each weekend checkin will be for the same week whether the week starts on Saturday or Sunday. Anyway, that is how I understand it.
SBtS