How long is the Tribulation?

The Tribulation covers a full seven year period, which is described as the covenant the antichrist makes with many for one week (a week of years). Daniel 9:27 says, "And he shall confirm the covenant with many for one week: and in the midst of the week he shall cause the sacrifice and the oblation to cease." That seven year span is split evenly in two.

The first three and a half years are called the beginning of sorrows. This is the time of false messiahs, wars, famines, earthquakes, and the early persecution of believers described in Matthew 24:5-8. During this half, Israel is not yet opposing the antichrist, because he is allowing them to rebuild the temple and resume their sacrifices, acting as though he were their deliverer.

The second three and a half years is the Great Tribulation itself, and it runs to the midpoint of the seven years and beyond. It begins when the antichrist breaks the covenant, enters the temple, sits on the mercy seat, and demands worship as God, which is the abomination of desolation spoken of by Daniel and by Jesus in Matthew 24:15. This second half is described as being allowed to continue for forty two months, according to Revelation 13:5, which is exactly three and a half years. This is the time of the worst persecution, the time Jesus called great tribulation such as was not since the beginning of the world, and it runs until the days are shortened for the elect's sake, followed by the darkening of the sun and moon, the falling of the stars, and the appearing of the sign of the Son of man.

So altogether, the Tribulation lasts seven years, made of two three and a half year halves: the beginning of sorrows first, and then the Great Tribulation, which ends with the antichrist's actions in the temple and the coming of the Lord to gather His elect.