'Great Tribulation' in the Bible

And I applied my heart to seek and to search out by wisdom concerning all that is done under heaven. It is a great tribulation that God has given to the sons of men to be exercised therewith.

for then there will be great tribulation, such as not has happened from the beginning of the world until now, nor, no, it will not happen.

Behold, I throw her into a bed, and those who commit adultery with her into great tribulation, if they do not repent of her works.

And I said to him, My lord, thou know. And he said to me, These are those coming out of the great tribulation, and they washed their robes, and made them white in the blood of the Lamb.