"Immediately after the tribulation of those days shall the sun be darkened, and the moon shall not give her light." Matthew 24:29.
The "tribulation" is often confused with the "time of trouble" spoken of in Daniel 12:1, which takes place in the last days. The two periods are actually separated by more than 200 years. The word "tribulation" denotes a persecution of God's people. "The tribulation" spoken of by Jesus has already taken place, during the dark ages. The "time of trouble," on the other hand, will be the period of God's wrath upon those who ultimately refuse His mercy.
"Those days" in Matthew 24:29 is a reference to the 1260-day prophecy (538-1798). The "tribulation of those days" was the portion of that prophecy in which God's people were persecuted. The most significant historical event to bring the persecution to an end was the establishment of the United States of America as a land of religious liberty. In 1776 the Declaration of Independence was signed, stating that "all men are created equal, that they are endowed by their Creator with certain unalienable rights, that among these are life, liberty, and the pursuit of happiness." America opened her doors to all who sought religious freedom, guaranteeing the right of all to worship according to their own conscience. Thus the persecution of those days was shortened for the elect's sake (Matthew 24:22).
Jesus, therefore, precisely identified when the sun would be darkened:
"But in those days (538-1798), after that tribulation (after 1776), the sun shall be darkened, and the moon shall not give her light." Mark 13:24.
It had to take place shortly after 1776, and before 1798. True to Christ's prediction, the sun was darkened on May 19, 1780.