The boy Joseph Smith was visited by Moroni, an angel. This was some of what he said:

"For behold, the day cometh that shall burn as an oven, and all the proud, yea, and all that do wickedly shall burn as stubble; for they that come shall burn them, saith the Lord of Hosts, that it shall leave them neither root nor branch. Behold, I will reveal unto you the Priesthood, by the hand of Elijah the prophet, before the coming of the great and dreadful day of the Lord. And he shall plant in the hearts of the children the promises made to the fathers, and the hearts of the children shall turn to their fathers. If it were not so, the whole earth would be utterly wasted at his coming." Joseph Smith continues..."he informed me of great judgements which were coming upon the earth, with great desolations by famine, sword, and pestilence; and that grievous judgements would come on the earth in this generation."

In Joseph Smith - Matthew it states:

"So likewise, mine elect, when they shall see all these things, they shall know that he is near, even at the doors; But of that day, and hour, no one knoweth; no, not the angels of God in heaven, but my Father only."