Double Mastery Weekend in NYC occurred from October 24, 2009 to October 25, 2009. In New York, mastery percentage per job performed was doubled. A glitch during this Event caused some job mastery percentage bars to disappear. Performing jobs that suffered this glitch could result in either 100% level mastery of them regardless of the previous percentage, or less fortunately, it could result in further mastery percentage on that job being locked.