There are many different types of latter day prophets running around today with a "word from the Lord" for mankind, or for specific areas of the world, or with a word about America's present spiritual condition and about her future. Many of them claim to have apocalyptic dreams and visions of the future, or else have some secret, hidden knowledge given to them about a dire future judgement of calamities, wars, pestilence, etc. etc.
How do we know which prophets to believe and which ones are simply blowing smoke? Well, I could tell you which ones not to listen to if they claim to have some secret esoteric knowledge imparted to them alone, apart from the Word of God: All of them. And I could tell you which ones know exactly when the Lord is coming back: None of them.
Our Lord Himself told us that He would come back unexpectedly, and that we would not know if it would be in the evening, in the middle of the night, or when the cock crows in the morning. So we should be ready at all times for His coming. As He instructed us: "Watch and pray".
There are generally two types of end time prophets who have garnered much attention in the Christian world today. The first type are the ones who preach the "pre-tribulation" rapture. Basically this is the belief that in the near future there will be a seven year period of intense suffering for most of mankind, except for those who have responded to an alter call and asked Jesus to forgive their sins and accepted Him as Lord and Saviour, or else have been led to the Lord by some other ministry, or even in the privacy of their own homes when being drawn and convicted by the Holy Spirit have asked our Lord to forgive them and save them from their sins. Many of these people go to church regularly and keep up appearances as born again Christians. I can't say how many of these people really know the Lord; our Lord said that if we truly love Him we would keep His commandments. I do know that there are undoubtedly many people in many church denominations who have responded to alter calls who are sincere believers who love Jesus with all of their hearts. I personally think the pre-tribulation rapture theory is possibly in error, but many people who believe in it love the Lord, so whether you believe the church will go through the tribulation or not should never be a test of your Christian orthodoxy.
The second type of end time prophets are those who are known as "post" or "mid" tribulation prophets. Generally these teachers believe that the church will go through all or part of the tribulation period, and also go through intense suffering and persecution. I tend to go along with this viewpoint, but I cannot say exactly when these calamities and persecutions will start. I actually believe that we are entering into the last days now, and that the persecution that genuine Christians will go through is already at hand, even at the door. I believe that it is time for us to gird up our loins, to be ready to endure, to begin to seek the Lord with fasting, earnest prayers and supplications, so that we may be delivered from the judgements to come. I believe that the coming of our Lord is very close, even at the door. I believe that we need to prepare ourselves, that the bride of Christ needs to repent, to turn from sin and worldliness, and humble herself, for the coming of our Lord may be nearer than we think.
I can't say what kind of calamities might come to pass outside of the Word of God.
A favorite prophecy of end time post-tribulation preachers is that California is going to fall off into the ocean, which is scaring the socks off of some folks who take this kind of thing seriously. There is one so-called end time prophet who claims that out of all of the millions of people living in Los Angeles, the Lord singled him out and told him to move to another state to avoid the catastrophic destruction of California. Whatever it was that drove him to flee for his life from California to safer digs, whether it was a real warning from the Lord or his own delusional imagination, we know that it was precisely the opposite instruction that Jonah received when God was preparing to destroy Nineveh. I would think that if God were really preparing to destroy a large chunk of Southern California, then it would be a prophets' duty to stay with the multitude and preach repentance to them. Surely there are many decent families, innocent children and helpless people in old age homes who would need someone to stick around and share the word of God with them, instead of running like a scared rabbit for his own life away to the mountains. In addition, there are many mentally and physically infirm people in Southern California who would need somebody to help them during a catastrophe, and to lead them to the Lord. The scripture says that the true shepherd gives his life for the sheep, but a false shepherd, when he sees the wolf (danger) coming, skeedaddles for his own life and leaves the sheep on their own to perish. Perhaps a spirit of self-sacrifice would be more in line for a true prophet than fleeing off to his little bungalow in the mountains of Montana or Wyoming.
Another popular topic among end time preachers is that some particular individual is going to be the antichrist, and this target has changed focus over the years, going from one world leader to another for many years, even for centuries. I think that undoubtedly many world leaders have had antichrist tendencies, and that some of them may have even been candidates for being "the" antichrist, but our Lord has kept this nefarious individual back by the Hand of His Spirit until the times will come. I know that there are dark forces at work in the world today, but that we are not meant to fear them, because "Greater is He who is in you, than he who is in the world". Our Lord told us not to fear, because not a hair of our heads shall perish. God will take care of His own.
So no matter what seems to be going on in the world today, no matter how dark the situation seems, remember that God is ultimately in control, and as Noah Hutchins says, "God is still on the throne and prayer changes things", and that He knows those who are His, and that He will send His angels to bear those up who trust in Him with all of their hearts, and that He will shelter them with His feathers, and cover them with His wings. Our Lord said, "Fear not little flock, you are of much more value than the sparrows", and if our Heavenly Father feeds them, then how much more will He take care of you, the flock of his pasture?