Charles Taze Russell, the founder of the Watchtower, believed that the "sign in the sun, moon and stars" of Matthew 24:29 had their fulfillment in two mysterious events that occurred in 1780 and 1833.
1780
"Are these signs to be regarded as literal or as symbolic? and have they yet been fulfilled? We answer that they have had a literal fulfilment, and are now having a symbolic fulfilment much more momentous. On May 19, 1780 (still 'in those days,' the 1260 years of Papal power, but after that power had begun to wane and the brunt of the tribulation had passed) a phenomenal darkening of the sun occurred, for which scientists of that time and since have never been able to account.. This unaccountable day, except as a sign from the Lord, is reckoned to have extended over 320,000 square miles - an area about twenty-five times the size of Palestine, to which the signs of the first advent were limited. Indeed, the fact that these signs were chiefly confined to the New England and Middle States need not surprise us, when we remember that the first movement amongst the 'Virgins'* (Matt. 25:1-5) was chiefly in the same locality. And that God should use the 'land of liberty' for sending the message of these signs to the world, is no more wonderful than that he has been pleased to send from the same quarter many of the modern blessings and inventions and lessons, recognized by the whole world, and aptly emblemized by the gift of the great French artist, Bartholdi, to New York harbor - the statue of 'Liberty Enlightening the World.'" {BATT 585-8}
BATT
C.T.Russell: Studies in the Scriptures IV - Battle of Armageddon (till 1910, The Day of Vengeance), 1897, 1904-20, 1923-5, 1927