What is the tribulation? How do we know that the end times tribulation will last seven years? What eschatological events occur during the tribulation period?

Links:

What is the tribulation? - https://www.gotquestions.org/tribulation.html

What is the Great Tribulation? - https://www.gotquestions.org/Great-Tribulation.html

What are the seventy sevens in Daniel 9:24-27? - https://www.gotquestions.org/seventy-sevens.html