Background: Odom was born in South Jamaica, Queens, New York City, to Joe Odom and Cathy Mercer. His father was a heroin addict, and Odom's mother died of colon cancer when he was twelve years old. At her deathbed, Odom's mom told him: "Be nice to everybody". Afterwards, he was raised by his maternal grandmother, Mildred Mercer.
Context: On December 11, 2011, Odom was traded to the Dallas Mavericks, the defending NBA champions, for a first-round draft pick and an $8.9 million trade exception after NBA Commissioner David Stern vetoed a proposed three-team trade that would have sent Odom and Houston Rockets teammates Kevin Martin, Luis Scola, and Goran Dragic to the New Orleans Hornets; Chris Paul to the Lakers; and Pau Gasol to the Houston Rockets. Odom felt "disrespected" after he learned of the Hornets trade publicly, and he requested a trade from the Lakers to another contending team. The Lakers were also concerned that Odom's contract was pricey since he was not needed to initiate the triangle offense with Mike Brown replacing Phil Jackson as Lakers coach.  In January 2012, Sports Illustrated reported that "Odom [had] yet to find his niche in Dallas. His struggles [made] him a frequent target of [Mavericks coach Rick] Carlisle, who [harped] on Odom's need to understand the coverages, be more alert, communicate and get in better shape... Team sources say Odom...appeared stressed by what they believe [was] the mental burden of an overwhelming offseason." On March 2, 2012, Odom was assigned to the Texas Legends of the NBA D-League. He had missed the prior three games due to personal reasons. His stint with the Legends was canceled on March 3, 2012, and he returned to the Mavs' active roster. On March 24, Odom did not play in a 104-87 loss to the San Antonio Spurs; this was the first time he could remember not playing due to a coach's decision.  On April 9, 2012, it was announced that Odom had parted ways with the Mavericks. Instead of releasing him, the team listed Odom as inactive for the remainder of the season. The move allowed the Mavericks to trade him at the end of the season. In a statement to ESPN, Odom said, "I'm sorry that things didn't work out better for both of us, but I wish the Mavs' organization, my teammates and Dallas fans nothing but continued success in the defense of their championship." Mavericks owner Mark Cuban admitted that a clash between the two during halftime in a game against the Memphis Grizzlies on April 7 was the last straw. Odom reportedly responded angrily when Cuban questioned his commitment, asking if he was "in or out." Odom averaged only 6.6 points in 20.5 minutes along with career lows in shooting percentage (35.2), rebounds (4.2) and assists (1.7) .
Question: When did Odom join the Mavericks?

Answer:
On December 11, 2011,