This might help:
Daniel 9:27 gives a few highlights of the seven-year tribulation period: “He will confirm a covenant with many for one 'seven.' In the middle of the 'seven' he will put an end to sacrifice and offering. And on a wing of the temple he will set up an abomination that causes desolation, until the end that is decreed is poured out on him.” The person of whom this verse speaks is the person Jesus calls the “abomination that causes desolation” (Matthew 24:15) and is called “the beast” in Revelation 13. Daniel 9:27 says that the beast will make a covenant for seven years, but in the middle of this week (3 1/2 years into the tribulation), he will break the covenant, putting a stop to sacrifice. Revelation 13 explains that the beast will place an image of himself in the temple and require the world to worship him. Revelation 13:5 says that this will go on for 42 months, which is 3 1/2 years. Since Daniel 9:27 says that this will happen in the middle of the week, and Revelation 13:5 says that the beast will do this for a period of 42 months, it is easy to see that the total length of time is 84 months or seven years. Also see Daniel 7:25, where the “time, times, and half a time” (time=1 year; times=2 years; half a time=1/2 year; total of 3 1/2 years) also refers to “great tribulation,” the last half of the seven-year tribulation period when the beast will be in power.
https://www.gotquestions.org/tribulation.html