The ATP Rankings, as defined by the Association of Tennis Professionals (ATP), are the "objective merit-based method used for determining qualification for entry and seeding in all tournaments for both (male) singles and doubles, except as modified for the ATP World Tour Finals (singles or doubles)." The rankings period is "the immediate past 52 weeks, except for: Barclays ATP World Tour Finals, singles and doubles, which is dropped on the Monday following the last ATP World Tour event of the following year; Futures Series tournaments that are only entered into the system on the second Monday following the tournament's week. Once entered, all tournaments, except the Barclays ATP World Tour Finals, remain in the system for 52 consecutive weeks."