Thought I had blocked dates. Turns out I had just added a note to the date range.
My rookie mistake trying to block dates was this: Selected date range; clicked on "block"; clicked on notes and inserted my sons name to remember that I was blocking out the dates he would be home; FORGOT to click on "save";
A line with my son's name appeared across the date range. It appeared to me that the calendar had reserved my blocked range. It was only when someone reserved a week in that month that I realized that the line across the date range was just a note.
The rules for making a note and blocking dates are different. The note appears without "save." Dates are actually blocked only after the "save". Now I know that a blocked range shows diagonal lines on the dates IN ADDITION to the line with the note.