Title: Houston Astros
Content:  The Houston Astros are an American professional baseball team based in Houston. The Astros compete in Major League Baseball (MLB) as a member club of the American League (AL) West division, having moved to the division in 2013 after spending their first 51 seasons in the National League (NL). The Astros were established as the Houston Colt .45s and entered the National League as an expansion team in along with the New York Mets. The current name, reflecting Houston's role as the host of the Johnson Space Center, was adopted three years later, when they moved into the Astrodome, the first domed sports stadium and the so-called 
Title: American League
Content: Houston Astros enfranchised 1962 in National League as the Houston Colt .45s (team changed name to Astros in 1965), transferred to American League (2013) ; Los Angeles Angels enfranchised 1961 as the Los Angeles Angels, then as the California Angels after moving to Anaheim (1966), then the Anaheim Angels (1997), then the Los Angeles Angels of Anaheim (2005). This last remains the legal name of the franchise, but in actual practice, the team is known as the Los Angeles Angels. ; Oakland Athletics enfranchised 1901 in Philadelphia, moved to Kansas City (1955) and to Oakland (1968) ; Seattle Mariners enfranchised 1977 ; Texas Rangers enfranchised 1961 as the Washington Senators, moved to Arlington, Texas (1972) 
Title: National League
Content: 1953: Boston Braves move to Milwaukee ; 1958: Brooklyn Dodgers move to Los Angeles and New York Giants move to San Francisco ; 1962: Houston Colt .45s and New York Mets enfranchised ; 1965: Houston Colt .45s renamed Astros ; 1966: Milwaukee Braves move to Atlanta ; 1969: Montreal Expos and San Diego Padres enfranchised ; 1993: Colorado Rockies and Florida Marlins enfranchised ; 1998: Arizona Diamondbacks enfranchised ; 1998: Milwaukee Brewers transfer from the American League. (Before the 1998 season, the American League and the National League each added a fifteenth team. Because of the odd number of teams, only seven games could possibly be scheduled in each league on 
Title: Houston Astros
Content:  to move the Astros to the American League. In October later that year, Crane met personally with MLB Commissioner Bud Selig, in a meeting that was described as "constructive". On November 15, 2011, it was announced that Crane had agreed to move the franchise to the American League for the 2013 season. The move was part of an overall divisional realignment of MLB, with the National and American leagues each having 15 teams in three geographically balanced divisions. Crane was given a $70 million concession by MLB for agreeing to the switch; the move was a condition for the sale 
Title: History of the Houston Astros
Content:  divisional realignment of MLB, with the National and American leagues each having 15 teams in three geographically balanced divisions. Crane was given a $70 million concession by MLB for agreeing to the switch; the move was a condition for the sale to the new ownership group. Two days later, the Astros were officially sold to Crane after the other owners unanimously voted in favor of the sale. It was also announced that 2012 would be the last season for the Astros in the NL. After over 50 years of the Astros being a part of the National League, this move was unpopular with many Astros fans.
Title: History of the Houston Astros
Content:  The Houston Astros are an American professional baseball team based in Houston, Texas that competes in Major League Baseball (MLB). The Astros are a member of the MLB's American League, having moved from the National League in 2013. The Astros are one of two MLB teams based out of Texas, the other being the Texas Rangers. The team began with the name of the Colt .45s in 1962 and changed their name to the Houston Astros in 1965 when they began playing in the Astrodome. The team has played in three ballparks in Houston, Colt .45 Stadium (1962–1964), the Astrodome (1965–1999), and, currently, Minute Maid Park (2000–), a stadium with a retractable roof. The Astros hold one World Series title and four pennants (one in the National League and three in the American League).
Title: Houston Astros
Content:  over 50 years of NL play with a 5–4 loss to the Chicago Cubs and began to look ahead to join the American League. Winning only 20 road games during the entire season, the Astros finished with a 55–107 record, the worst record in all of Major League Baseball for the 2012 season, and surpassing the 2011 season for the worst record in Astros history. On November 2, 2012, the Astros unveiled their new look in preparation for their move to the American League for the 2013 season. The navy and orange uniform returned to the original 1960s team colors, 
Title: 2005 National League Championship Series
Content:  This series was the unofficial end of the Astros and Cardinals rivalry that developed when the Astros moved to the National League Central in 1994. From 1996 to 2006, either the St. Louis Cardinals or the Houston Astros won the National League Central every year, except for 2003. Both teams also played each other in dramatic and compelling National League Championship Series in 2004 and 2005. After the 2006 season, both teams had older rosters, but went in opposite directions. The Astros embarked on a long re-build and eventually moved from the National League to the American League after the 2012 season. To get themselves on the winning track again, 
Title: Houston Astros
Content:  Wonder of the World." The Astros moved to a new stadium called Minute Maid Park in 2000. The Astros played in the NL West division from 1969 to 1993, then the NL Central division from 1994 to 2012, before being moved to the AL West as part of a minor realignment in 2013. The Astros posted their first winning record in 1972 and made the playoffs for the first time in 1980. The Astros made their first World Series appearance in 2005 but were swept by the AL’s Chicago White Sox. In the following decade, the team embraced sabermetrics and pioneered new analytical technologies during the early 
Title: National League Division Series
Content:  NOTE: With the Houston Astros move to the American League at the conclusion of the 2012 season, the Braves vs Astros series is not currently possible.

Question: when did the astros change from the national league to the american league?
Answer: 2013.
March 31, 2013.