As I have reflected on this matter the last few weeks, I've thought to myself,
1-"how do they know?"
2- "what brought them to this conclusion?" There are a lot of people out there that got this from doing math from the Bible and other resources, but as I have studied about this and pondered about it, a scripture kept coming to mind, the scripture is found in D&C 49:7
"I, the Lord God, have spoken it; but the hour and the day no man knoweth, neither the angels in heaven, nor shall they know until he comes."
Also in Matthew 24:36
"But of that day and hour knoweth no man, no, not the angels of heaven, but my Father only."Only God knows when Jesus Christ will come! and that is what I rely on! I have faith in my God and know that He is preparing His people for that time,which no man knoweth.
Thomas S. Monson (check out the link to find out more about him!) and I also know that as it states in Amos 3:7:"Surely the Lord God will do nothing, but he revealeth his secret unto his servants the prophets."
I know that as we continue to listen to the Prophet and follow his counsel, we need not be afraid! He will prepare us for what will happen. Trust in him. He cannot lead us astray!