A major portion of Paradise Lost is narrated by the angel Raphael. He begins his story with a celebration in heaven. In the chronology of PL, and even possibly the Bible, this can be said to be the earliest recorded eventóbefore the creation of the world, and before the war in heaven.

THE BIBLE: King James Version

Psalms II

6 Yet have I set my king upon my holy hill of Zion.
7 I will declare the decree: the LORD hath said unto me, Thou art my Son; this day have I begotten thee.

Hebrews I

1 God, who at sundry times and in divers manners spake in time past unto the fathers by the prophets,
2 Hath in these last days spoken unto us by his Son, whom he hath appointed heir of all things, by whom also he made the worlds;
3 Who being the brightness of his glory, and the express image of his person, and upholding all things by the word of his power, when he had by himself purged our sins, sat down on the right hand of the Majesty on high:
4 Being made so much better than the angels, as he hath by inheritance obtained a more excellent name than they.
5 For unto which of the angels said he at any time, Thou art my Son, this day have I begotten thee? And again, I will be to him a Father, and he shall be to me a Son?
6 And again, when he bringeth in the firstbegotten into the world, he saith, And let all the angels of God worship him.
THE BIBLE: Contemporary English Version

Psalms II

6 "I've put my king on Zion, my sacred hill."
7 I will tell the promise that the LORD made to me: "You are my son, because today I have become your father.
Hebrews I

1 Long ago in many ways and at many times God's prophets spoke his message to our ancestors.
2 But now at last, God sent his Son to bring his message to us. God created the universe by his Son, and everything will someday belong to the Son.
3 God's Son has all the brightness of God's own glory and is like him in every way. By his own mighty word, he holds the universe together. After the Son had washed away our sins, he sat down at the right sidea of the glorious God in heaven.
4 He had become much greater than the angels, and the name he was given is far greater than any of theirs.
5 God has never said to any of the angels, "You are my Son, because today I have become your Father!" Neither has God said to any of them, "I will be his Father, and he will be my Son!" 6When God brings his first-born Son into the world, he commands all of his angels to worship him.