David Letterman announced April 3 that he's retiring from CBS' "Late Show" after 21 years of hosting the program.

Letterman, the longest running late-night talk show host in U.S. TV history, said, there's no specific end date yet. "We don't have the timetable for this precisely down. I think it will be at least a year or so, but sometime in the not too distant future."

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