Hi Zeb,
The bloody bastards thought they had that one covered, too.
An extract from the Watchtower of 15th August 1968 ("Why are you looking forward to 1975?") stated:
This is not the time to be toying with the words of Jesus that "concerning that day and hour nobody knows , neither the angels of the heavens nor the Son, but only the Father." (Matt. 24:36)
Oh yeah, those that didn't swallow Crazy Fred's story about 1975 were indeed conspicuous by their silence during those years!