Is 2009 the last year in the decade?

no. The last year of a decade always ends in zero. The first decade started at year 1 and was 10 years long (year 1-10). Every decade to follow starts with a year ending with 1 and ends with a year ending in 0. The first day of this decade was January 1, 2001 and the last day will be December 31, 2010.