Albert Barnes Commentary 2 Kings 25:8

"Now in the fifth month, on the seventh day of the month, which was the nineteenth year of king Nebuchadnezzar, king of Babylon, came Nebuzaradan the captain of the guard, a servant of the king of Babylon, unto Jerusalem." — 2 Kings 25:8 (ASV)

The nineteenth year of king Nebuchadnezzar - This was 586 B.C. if we count from the actual date of his accession (604 B.C.), but 587 B.C. if, like the Jews, we consider his reign to have begun when he was sent by his father to recover Syria and won the battle of Carchemish (in 605 B.C.).

Captain of the guard - This literally means “the chief of the executioners” (Genesis 37:36).