It helps to know the Jewish wedding traditions of the time: after a man proposed marriage and the woman accepted, he went to his father's house to build on a room for them. No one knew when it would be done, because the father didn't know how long it would take the son to finish the job and the son didn't know how long it would take for the father to approve it. During this time the bride had to always be ready to go at a moment's notice, for no matter what time of day or night the pronouncement was made by the father, the son would leave immediately to get her.
Jesus was simply using the customs of the time to illustrate a spiritual principle, as he did many other times re. parables. The emphasis here is not on Jesus failing to be divine but on the need for his followers to always be ready, just as a bride can hardly wait to see her groom.
Consider also that this is about the exact day and hour, not the "season". Jesus scolded people for not "reading the signs of the times" and recognizing when the Messiah was to arrive. In Mt. 24:33 he said "Even so, when you see all these things, you know that it is near, right at the door." Later, the apostle Paul said:
Now, brothers, about times and dates we do not need to write to you, for you know very well that the day of the Lord will come like a thief in the night. While people are saying, “Peace and safety,” destruction will come on them suddenly, as labor pains on a pregnant woman, and they will not escape. But you, brothers, are not in darkness so that this day should surprise you like a thief. You are all sons of the light and sons of the day. We do not belong to the night or to the darkness. So then, let us not be like others, who are asleep, but let us be alert and self-controlled. (1 Thes. 5:1-6)

