<P> The MLB waiver deadline is August 31 . There is much less activity between August 1 and August 31 because players must clear waivers . The waivers are revocable meaning that a team can revoke the claim of another team on their player . Players may be acquired after the August 31 deadline; however, while they can contribute to a team's push for the playoffs, they are ineligible for postseason play . </P> <P> The trade deadline was instituted by MLB in response to various attempts by two New York City - based ballclubs, the Giants and Yankees, to use their financial advantages to tilt their respective leagues' competitive balance in their favor from 1917 through 1922 . In the Yankees' case, most of its dealings were with the Boston Red Sox . The American League (AL) established MLB's first - ever such rule in 1920 as an indirect result of the Red Sox's sale of Babe Ruth to the Yankees . It prohibited the trading and selling of ballplayers between August 1 and the conclusion of the World Series . A uniform rule serving both major leagues, which was adopted prior to the 1923 season, set the deadline at June 15 . The date, chosen by MLB Commissioner Kenesaw Mountain Landis based on a suggestion from Pittsburgh Pirates owner Barney Dreyfuss, remained in effect through the 1985 season . The rule originated with the 1986 Basic Agreement which resulted from the resolution of the 1985 MLB strike . </P> <P> The National Basketball Association's deadline falls on the 16th Thursday of the season (usually in mid-February) at 3pm Eastern Time . The deadline for the 2011 - 12 season was on March 15, 2012 due to the 2011 - 12 NBA lockout . In the NBA, post-deadline trades are forbidden, although teams are allowed to sign free agents and call up players from the G - League until the end of the regular season . </P> <P> The National Football League's deadline is the Tuesday following the eighth week (formerly sixth) of the regular season . </P>

When do the nba trades go into effect