Background: Dwayne Douglas Johnson was born on May 2, 1972 in Hayward, California, the son of Ata Johnson (nee Maivia) and professional wrestler Rocky Johnson (born Wayde Douglas Bowles). His maternal grandfather, "High Chief" Peter Maivia, was also a wrestler, and his maternal grandmother, Lia Maivia, was one of wrestling's few female promoters, taking over Polynesian Pacific Pro Wrestling after her husband's death in 1982, until 1988. Johnson's father is Canadian, of Black Nova Scotian, and a small amount of Irish, descent. His mother is of Samoan ancestry.
Context: The Rock's entertaining promos and ensuing popularity led to a face turn, in which he called himself "The People's Champion". This led to a feud with Mr. McMahon, who said he had "a problem with the people" and would thus target "The People's Champion". A double turn occurred at Survivor Series, when The Rock defeated McMahon's associate, Mankind, in the finals of the "Deadly Game" tournament for the vacant WWF Championship in a fashion reminiscent of the Montreal Screwjob. The Rock allied with Vince and Shane McMahon as the crown jewel of their stable, The Corporation. On December 13, 1998 at the pay-per-view named for him, Rock Bottom: In Your House, The Rock had a rematch with Mankind for the WWF Championship. Mankind appeared to win the match when The Rock passed out in the Mandible Claw submission move, but Mr. McMahon ruled that since The Rock did not tap out, he retained his title. The Rock continued to feud with Mankind over the WWF Championship, which was traded back and forth between them. First, in the main event of the January 4, 1999 episode of Raw Is War, Mankind defeated The Rock after interference from Stone Cold Steve Austin. Then, in an "I Quit" match at Royal Rumble on January 24, The Rock regained the title, when a recording of Mankind saying "I quit" from an earlier interview was played over the PA system. On Halftime Heat (an episode of Sunday Night Heat aired in the same timeslot as the Super Bowl XXXIII halftime show) on January 31, Mankind pinned The Rock using a forklift truck in an empty arena match. The two faced off again at St. Valentine's Day Massacre: In Your House in a last man standing match which ended in a draw, meaning Mankind retained the title. Their feud ended on February 15 Raw Is War, when The Rock won his third WWF Championship in a ladder match after Big Show performed a chokeslam on Mankind off the ladder. The Rock lost the WWF Championship to Stone Cold Steve Austin at WrestleMania XV. Though he was a villain, his amusing verbal skills led many fans to cheer The Rock, who then lost the title rematch at Backlash: In Your House and was thus betrayed by Shane McMahon, turning him back into a fan favorite and beginning a feud with Triple H, The Undertaker and The Corporate Ministry that saw The Rock defeating Triple H at Over the Edge, but then losing to WWF Champion The Undertaker at King of the Ring. The Rock lost a number one contender's match to Triple H at Fully Loaded after interference from Mr. Ass. This sparked a feud with Mr. Ass, culminating in a Kiss My Ass match at SummerSlam, which The Rock won. CANNOTANSWER
Question: When did he join the corporation. Whats the answer?

On December 13, 1998