While stated that the murder in this episode was the first of the millennium, the year 2000 is apart of the 20th Century not the 21st Century. The new millennium didn't start until January 01, 2001. While the episode is factually incorrect, so was much of the world, at the time.
Victim tells his wife he'll see her next century, but the date was Midnight 1999/2000 and the new century won't start till 2001.