This verse has always been difficult to understand. If Jesus was God, how could He be ignorant of the time of His second coming? Indeed He was, and is, God, but He also was, and is, man. This is a part of the mystery of the divine/human nature of Christ. In the gospel record, we see frequent evidences of His humanity (He grew weary, for example, and suffered pain), but also many evidences of deity (His virgin birth, His resurrection and ascension, as well as His perfect words and deeds).
He had been in glory with the Father from eternity (John 17:24), but when He became man, "in all things it behoved him to be made like unto his brethren" (Hebrews 2:17), except for sin. As a child, He "increased in wisdom and stature" like any other human (Luke 2:52). Through diligent study (as a man), He acquired great wisdom in the Scriptures and the plan of God. After His baptism and the acknowledgment from heaven of His divine Sonship (e.g., Matthew 3:16-17), He increasingly manifested various aspects of His deity, but He still remained fully human.
With respect to the time of the end, this depends in some degree on human activity. For example, He said that "the gospel must first be published among all nations" (Mark 13:10), and only God the Father could foresee just when men will have accomplished this. Although the glorified Son presumably now shares this knowledge, in His self-imposed human limitations, He did not.
In no way does this compromise His deity. In our own finite humanity, we cannot comprehend fully the mystery of the divine/human nature of Christ, but He has given us more than sufficient reason to believe His Word! HMM http://www.icr.org/article/5903/