usage, the first day of regular season
competition for any sports team or league. The most common usage, though, is for baseball
Major league Opening Day is probably the second-biggest sporting day in the United States, behind the Super Bowl. The first pitch of the season is always in Cincinnati, Ohio, home of the first professional team (the Cincinnati Red Stockings of 1869), starting a game hosted by the National League's Cincinnati Reds. The game normally starts around 1 PM Eastern time, and is quickly followed by a near-full slate of other games as other teams start their seasons. Opening Day games are almost always sold out, even if very few of that team's other home games are.
Starting in 1999, the major leagues decided to expand their worldwide marketing by conducting the first game of the season outside the continental U.S.; in 1999 and 2000, this was in Japan, and in 2001, the Toronto Blue Jays and Texas Rangers played their first game on 1 April in Puerto Rico. Nevertheless, most fans consider the true Opening Day to be the day the words "Play Ball!" are heard in Cincinnati.