http://www.youtube.com/watch?v=yJjpaceeb58

      In this link it is said when Christ used the words..."no man knows the day or hour", He was actually using a Hebrew idiom that was used to describe The Feast of Trumpets / Rosh Hashanah which was always the 1st day of the lunar moon in the 7th month, which was always the gathering of God's people.  If it were dark or overcast you couldn't see the new moon so that no one would know the day or hour.