The Colts celebrated their 65th anniversary in 2017. The franchise began in 1953 as the Baltimore Colts, an NFL team formed after the Dallas Texans franchise folded and its assets were transferred to Baltimore.
The Colts played in Baltimore for more than three decades and won major honors there, including the 1958 NFL Championship in a famous overtime game against the New York Giants. That contest is often called “The Greatest Game Ever Played” because it helped popularize professional football on television.
The team moved to Indianapolis in 1984 and became the Indianapolis Colts. Although the location changed, the NFL recognizes the franchise's continuous history, so the 2017 season counted as the Colts' 65th season in the league. It was the team's 34th season in Indianapolis.
The anniversary figure can be confusing because the Indianapolis identity began later than the franchise itself. Counting from the 1953 founding produces 65 seasons in 2017; counting only the years in Indianapolis would produce a different number. The Colts finished that 2017 season with a 4–12 record.