Is Jesus God?, page-608

In case you are wondering why only the Father only knew of the day and hour of the second coming of our Lord, it's the nature of the incarnation of Jesus. When the Word of God became flesh to dwell among the people, He remained fully God, but He also took on a true human nature. Jesus retained all the attributes of divinity, yet, as a man, He voluntarily restricted their use. This was part of the “self-emptying” or self-renunciation spoken of in Philippians 2:6–8. It stands to reason that when Jesus went back to be with His Father, He now knows when He will return.