What is the Lord's day?

"And I saw, coming out of the mouth of the dragon and out of the mouth of the beast and out of the mouth of the false prophet, three unclean spirits like frogs. For they are demonic spirits, performing signs, who go abroad to the kings of the whole world, to assemble them for battle on the great day of God the Almighty." - Revelation 16:13-14

Day of the Lord is also called the day of Armageddon in which Christ would face off and defeat the antichrist and all forces of opposition against God.

It is a day of great wrath also called the great day of God Almighty.

The battle against the antichrist is set to take place in Israel according to what I could conjecture from the Bible