If the abomination is to take place in 2018 like you are saying, than the trib would have to start in the next few months.
Nope, if the abomination takes place in 2018, the Tribulation begins in 2018...
Let's look at the Olivet Prophecy...
Mat 24:2 And Jesus said unto them, See ye not all these things? verily I say unto you, There shall not be left here one stone upon another, that shall not be thrown down.
Mat 24:3 And as he sat upon the mount of Olives, the disciples came unto him privately, saying, Tell us, when shall these things be?
and what shall be the sign of thy coming, and of the end of the world?
This question is looking toward a singular event, THE sign that would mark the end of the age and lead up to Christ's coming...
First of all, general conditions that would begin and intensify from Christ's time up to the end of the age are noted in Mat 24:4-14 with the Gospel of the Kingdom of God being preached in all the world but this is not a singular event. The very next event that occurs IS the singular event...
Mat 24:15 When ye therefore shall see the abomination of desolation, spoken of by Daniel the prophet, stand in the holy place, (whoso readeth, let him understand
A lot of speculation is extant about the AoD but please notice that Christ said it will be like the event that Daniel prophesied of. What was that event?
Then it happened: "On the fifteenth day of the month Kislev in the year 145" (verse 54, TEV), which corresponds to 168/167 B.C., "they set up the abomination of desolation upon the altar" of the temple (verse 54, KJV). This appears to have been a pagan altar, probably with an image representing the Greek chief god Zeus, as 2 Maccabees:6:2 tells us that Antiochus defiled the Jewish temple "by dedicating it to the Olympian god Zeus" (TEV). After all, to the Greek mind the God of the Hebrews simply equated to the chief god in the Greeks' pantheon.
The above is from this article...
What Is the "Abomination of Desolation"? | United Church of God
Mat 24:16 Then let them which be in Judaea flee into the mountains:
Mat 24:17 Let him which is on the housetop not come down to take any thing out of his house:
Mat 24:18 Neither let him which is in the field return back to take his clothes.
Mat 24:19 And woe unto them that are with child, and to them that give suck in those days!
Mat 24:20 But pray ye that your flight be not in the winter, neither on the sabbath day:
Mat 24:21 For then shall be great tribulation, such as was not since the beginning of the world to this time, no, nor ever shall be.
The AoD is the sign that occurs in two parts...
Luk 21:20 And when ye shall see Jerusalem compassed with armies, then know that the desolation thereof is nigh.
When Jerusalem is surrounded by armies, then the desolation is near. (probably 30 days)
In Mat 24 we saw that a singular event is the AoD. It happened once (in type) and it will happen again (anti-type).
The original AoD was Antiochus IV Epiphanes (Epidimes) rearing up a statue of Jupiter Olympus and sacrificing swine on the Altar. Christ said that the AoD marking the end of the age would be like the event that Daniel spoke of. Type and anti-type.
So after this brief explanation of the AoD, notice in Mat 24:21, the Tribulation begins immediately after the AoD is set up.