Odd or Even Year Usage is simply a more specific way of referring to and describing Biennial Usage. Odd or Even Year Usage is termed as such based upon the years when the interval week or weeks are used. For example, and odd-year agreement could consist of a timeshare owner occupying the same week in 2005, 2007 and 2009.
It is important to note that in Right-to-Use agreements, where an owners is granted a fixed number of weeks to be used throughout a fixed number of years, the value of biennial or Odd or Even Year Usage timeshares is half that of the value of an agreement allowing for annual usage.