The importance of the year 1971

In "My Encounter with God: Part I" I wrote that the thought that I would have to prove the existence of God came to my mind in the year 1970. But why was it that the year was 1970, and why was it not instead 1967 or 1968? In my brief biography I have mentioned that I had my first mystical experience either in 1965 or in 1966. Even if it was in the year 1966, still 1970 were too late. So the thought could have come to my mind much earlier.