Both the Old and New Testaments contain multiple references to what is called the Day of the Lord. This Day is consistently referred to as a day of gloom and darkness, fear and trembling, dread and distress. Isaiah prophesied: Behold, the Day of the LORD cometh, cruel both with wrath and fierce anger, to lay the land desolate: and he shall destroy the sinners thereof out of it (Isaiah 13:9). The Day of the Lord refers to God's special interventions into the course of world events to judge His enemies, accomplish His divine purpose for restoring a covenant relationship with Israel, and final defeating Satan and his godless followers. This Book will prove that the Day of the Lord is more than just a single day, it is two days separated by the 1000-year Millennial Kingdom. In the New Testament, the apostle Paul uniquely identifies a Day of Jesus Christ, which is not the same as the Day of the Lord. By carefully studying the Old and New Testaments, it will be conclusively determined that the Day of Jesus Christ corresponds to the Rapture of the Saints. The 1st Day of the Lord is the Battle of Armageddon, and the 2nd Day of the Lord is the final battle between God Himself and Satan at the end of the Millennial Kingdom. The 7 Holy Feasts of Israel will be explained, different Rapture beliefs, and the Duration of the Great Tribulation to support all conclusions. Finally, Jewish Messianic beliefs and expectations will be used to confirm and support scriptural proof. The meaning and correct interpretation of the two Days of the Lord, the Day of Jesus Christ and the Rapture of the Saints will both unify and confirm events recorded in the Book of Revelation.