No One Knows the Day or Hour
This verse is the basis for the Pre-Tribulation Rapture, for it is the foundation of the imminent return of Christ. The reasoning is that the only way the timing of the Rapture can be unknowable is if it is prior to Daniel's seventieth week, for if it were in the middle or at the end of the seven year period, we would be able to mark the days off our calendars and come to the day (though perhaps not the hour) of His return. However, this cannot be true, for the prior context of this passage is not just of the Rapture, but the second coming of Christ in glory and power after the great tribulation.
The succeeding passage may indicate that though we do not presently know the day and hour of Christ's return, it does not mean we will never be able to know this in the future.