Background: Wilbur Charles "Weeb" Ewbank (May 6, 1907 - November 17, 1998) was an American professional football coach. He led the Baltimore Colts to NFL championships in 1958 and 1959 and the New York Jets to victory in Super Bowl III in 1969. He is the only coach to win a championship in both the National Football League (NFL) and American Football League (AFL).
Context: Ewbank moved back to Oxford in retirement and wrote a book in 1977 called Football Greats. He was inducted into the Pro Football Hall of Fame in 1978, but said later that year that he was glad to be out of coaching. With the expansion of the NFL, he said, talent had become diluted and fielding a good team was difficult. Coaches, meanwhile, customarily took the blame for a team's failures, and the sport had become too violent.  Ewbank's coaching style was laid-back but efficient, combining his mild personality with an orderliness inherited from Paul Brown. "Weeb combined a low-key style with a flair for the most dramatic of accomplishments", former NFL commissioner Paul Tagliabue said in 1998. "He led two of the legendary teams during the era of pro football's greatest growth. But he preferred to stay in the background and let the players take the credit." He favored well-practiced execution of a limited number of plays over complicated offensive and defensive systems. Paul Brown "had the exact same approach: Don't do too much, but what you do, execute it flawlessly", Raymond Berry said in 2013, adding that the Colts' 1958 championship team had only six passing plays.  Ewbank is the only man to coach two professional football teams to championships, and the only man to win the NFL championship, the AFL championship and a Super Bowl. Ewbank's regular-season career record in the NFL and AFL was 130-129-7, and his playoff record was 4-1. Ewbank was selected as the head coach on the AFL All-Time Team in 1970. In addition to the Pro Football Hall of Fame, he was inducted into the Miami University Athletic Hall of Fame in 1969, the Indiana Football Hall of Fame in 1974 and the Talawanda School District Athletic Hall of Fame in 1999. He also won the Walter Camp Distinguished American Award in 1987 and was inducted into the Jets' Ring of Honor in 2010.  Ewbank suffered a dislocated hip in the aftermath of the Jets' 1968 AFL championship game win, and had other health issues in his later years. He broke his leg and had two hip replacements in the 1990s. He also had myasthenia in his right eye. Ewbank died at 91 on November 17, 1998, the 30th anniversary of the "Heidi Game", after suffering from heart problems. He and his wife Lucy had three daughters.
Question: When did Weeb retire?

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