The Bible says:
"Let no man deceive you by any means. For that day shall not come, except there come a falling away first, and the man of sin be revealed, the son of perdition, who opposeth and exalteth himself above all that is called God or that is worshipped." - II Thesselonians 2:3,4
And our Lord Jesus says:
"But of that day or hour knoweth no man..." - Matthew 24:36
"Watch therefore, for ye know neither the day nor the hour wherin the Son of man cometh." - Matthew 25:13
"Therefore be ye also ready, for in such an hour as ye think not the Son of man cometh." - Matthew 24:44