Mark 13:32 (KJV) — But of that day and that hour knoweth no man, no, not the angels which are in heaven, neither the Son, but the Father.
It does not say "shall not know" the month or year but do not know (present tense) the day or hour. This phrase is actually the Hebrew idiom for the "Feast that no man knows the day or hour", that is, "Yom Teruah" / "Feast of Trumpets/Shouting". This is the only feast day that you do not know in advance exactly when it is going to start because it happens on the day of the new visible crescent moon of the 7th month.
The statement was never meant to say we could never know the timing of the the Messiah's coming in advance. That would conflict with many other scriptures if it were the intent. But Christians generally understand it to mean "dont set dates or get distracted studying prophecy", which is understandable since historically every past date for the reign of Messiah has been wrong.
Nevertheless, we were given the 70 weeks of Daniel and the Parable of the Fig Tree to "show his servants" the timing of these things in advance (See Rev 1:1-2). Moreover, there are any number of timing markers given in Daniel and Revelation which once you see them happen, you know that the Messiah's return will be in either 1290 days, 1260 days, 1335 days, 42 months or 3½ years from that point! Thus once you see the event you know the the timing of Second Advent down to year, month and day, as long as you can accurately handle counting the passing of days.
http://www.escapeallthesethings.com/no-man-knows-the-day-or-hour.htm