Abraham saw the day of Christ in his own time, because he understood the Scriptures. Consider Genesis 3:15, the statement of God to the serpent at the Fall of man – ‘I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heal.
He does not say, ‘Your father Abraham rejoiced that he would see my day.’ That rendering is a modification of the Lord’s statement that was made of the translators of the Revised Standard Version in the early 1950s, detracting from the weight and depth of the Lord’s statement, and is duly followed by the English Standard Version. Beware of the many of the materialistic translations that come all the way from the RSV. ‘Your father Abraham rejoiced to see my day’, not rejoiced that he would see my day. The King James translators following Tyndale are quite correct, and other modern translations that follow them in this. Abraham saw the day of Christ.