We are not given exact dates, but God has determined exact dates, whether we know it or not, is another matter, as he only reveals what he wishes to reveal, and sometimes when he does reveal, he reveals in obscurity of dreams, visions, and symbols. However, there have been times where God has revealed exact times, such as with the 70 weeks of Daniel, thus revealing exactly 490 years from the captivity of Babylon to the coming of the Messiah.