Monk graduated college in 1981. He met Trudy while in college. This is stated in the season 5 episode 6, "Mr. Monk and the Class Reunion." The whole reunion he kept saying he was referred to "as the guy with Trudy". However, in the video she makes for Monk, Trudy's states her pregnancy happens in 1982-1983. She says in the video it was years before she met Monk, but that would have been impossible.