Conversation so far:
What is Kenneth, what is the frequency? from?
On October 4, 1986, while walking along Park Avenue to his Manhattan apartment, Rather was attacked from behind by a man who demanded to know Kenneth, what is the frequency?“
Was Dan Rather hurt while walking along Park Avenue on October 4, 1986?
As the assailant pummeled and kicked Dan Rather, he kept repeating the question.
Did Dan Rather find the attackers from October 4, 1986?
In 1997, a TV critic writing in the New York Daily News solved the mystery, publishing a photo of the alleged assailant, William Tager.

Question: When did this happen?
Self-contained rewrite: When did the Kenneth, what is the frequency? attack happen to Dan Rather?