In 2009, the Indianapolis Motor Speedway began a three-year-long "Centennial Era" to celebrate the 100th anniversary of the opening of the track (1909), and the 100th anniversary of the first Indy 500 (1911). As a gesture to the nostalgic "Centennial Era" celebration (2009–2011), tickets for the 2009 race donned the moniker "93rd 500 Mile International Sweepstakes". It is the first time since 1980 that the "Sweepstakes" title has been used. During the month of May 2009, the ordinal (93rd) was used very sparingly, and for the first time since 1981, was not identified on the annual logo. Instead, in most instances in print, television, and radio, the race was referred to as the "2009 Indianapolis 500". Since the race was not held during the United States' participation in the two World Wars (1917–1918, 1942–1945), the advertised Centennial Era occurred during the 93rd to 95th runnings. To avoid confusion between the 100th anniversary, and the actual number of times the race has been run, references to the ordinal during the "Centennial Era" were curtailed.