2KI 24:8 Jehoiachin (Jehoiakim) was eighteen years old when he began to reign.
2CH 36:9 He was eight.
(Note: This discrepancy has been "corrected" in some versions.)
No contradiction, just a matter of understanding words:
Taken from "Age of the Earth" (my own personal study) -
https://archive.org/download/age-of-the-earth/Age of the Earth.pdf
What about Daniel 1:1-2; 2 Kings 24:1,6 and the age of Jehoiachin?
The 13th year of Josiah (AM 3599) unto the 1st year of Nebuchadnezzar (Jer 25:1, 46:2; AM 3617 - Jehoiakim + 4 (Jer 25:1) = AM 3621) is 23 years (Jer 25:3), inclusive reckoning (AM 3586 - Josiah + 13 (Jer 25:3) = AM 3599; thus AM 3599 (1) + 22 = 23 years; Jer 25:3; AM 3621))
AM 3586 - Josiah - AM 3617 (13th year is AM 3599)
AM 3617 - Jehoahaz - AM 3617
AM 3617 - Jehoiakim - AM 3628 (4th year is AM 3621, is 23 years inclusive (Jer 25:3), 1st year of Nebuchadnezzar; Jer 25:1, 46:2; Jehoiakim is 36 years old when taken captive (2 Chr 36:6) in AM 3628)
AM 3628 - Jehoaichin - AM 3628/9 (is the 8th year of Nebuchadnezzar's reign (2 Chr 24:12, 36:9-10; 2 Ki 24:8; Jer 24:1, 29:2; Eze 17:12))
AM 3629 - Zedekiah - AM 3640 (9th year is AM 3638, is the 17th year of Nebuchadnezzar (Jer 39:1, 52:5), thus AM 3621 – AM 3638 = 17 years)
Jehoiachin was 18 years old (2 Ki 24:8; AM 3628) when he began to reign, which makes Jehoiakim, his father, 36 years old at that time. This places Jehoiachin's birth 18 years previous in AM 3610, which makes Jehoiakim, his father, 18 years old at that time.
The 1st year of the captivity of Jehoiachin (2 Chr 24:12, 36:9-10 (
lit. 'a son of 8 years, under Nebuchadnezzar's reign'); 2 Ki 24:8 (Jehoiachin was 18 years of age
in the 8th year of Nebuchadnezar's reign; literally a "son of eight years" or "eight years old" under Nebuchadnezzar's reign, not actually 8 years in age, but in relation to the new King (see also 1 Samuel 13:1, literally "a son of one year"), meaning in subjection to the King of Kings Nebuchadnezzar)) Jer 24:1, 29:2; Eze 17:12; AM 3629) is the 8th year of the reign of Nebuchadnezzar.
The 5th year of the captivity of Jehoiachin (Eze 1:2; AM 3634) is in the 30th year, 4th month, 5th day (Eze 1:1; 30 years prior = AM 3604, middle of Josiah's reign AM 3586 - AM 3617, or the 18th year of Josiah's reign to be precise, the finding of the Law, the restoration of the Temple, and his covenant to God, see 2 Ki 22:3, 23:23; 2 Chr 34:8,31, 35:1-19).
The 9th year (10th month, 10th day) (Jer 52:4; AM 3638) of the reign of Zedekiah is the 17th year of the reign of Nebuchadnezzar, who at that time besieged the city of Jerusalem (Jer 39:1, 52:5), for two years ((9th) 80 + (10th) 360 + (11th) 99 = circa 539 days (30 day months)), unto the 11th year (4th month; 9th day) (Jer 39:2, 52:5-7).
The 10th year (AM 3639) of the reign of Zedekiah is the 18th year of the reign of Nebuchadnezzar (Jer 32:1), 832 persons of Jerusalem were carried captive to Babylon (Jer 52:29).
The 11th year (AM 3640) of the reign of Zedekiah is the 19th year of the reign of Nebuchadnezzar (2 Ki 25:2-8), (5th month, 10th day) (Jer 52:12), in which Zedekiah is blinded (2 Ki 25:7; Jer 39:7, 52:10-11; Eze 12:13) and taken captive.
In the 23rd year of the reign of Nebuchadnezzar (Jer 52:30; AM 3644), more persons, 745 Jews, are carried away captive to Babylon, all together 4,600 persons captive.
The 1st year of Evilmerodach was the 37th year of the captivity of Jehoiachin (Eze 1:2; AM 3634 (5th) + 32 = AM 3666), in the 12th month, 25th day (Jer 52:31; issued the orders to have him come “out of prison”), 27th day (2 Ki 25:27; orders actually carried out, and he comes out of prison, “did lift up the head … out of prison”), and Zedekiah was 21 years old when Jehoiachin was taken captive (2 Ki 24:18), which would make Zedekiah 58 years old in the first year of Evilmerodach if he was even still alive.
2 Kings 23:34 And Pharaohnechoh made Eliakim the son of Josiah king in the room of Josiah his father, and turned his name to Jehoiakim, and took Jehoahaz away: and he came to Egypt, and died there.
2 Kings 23:36 Jehoiakim was twenty and five years old when he began to reign; and he reigned eleven years in Jerusalem. And his mother's name was Zebudah, the daughter of Pedaiah of Rumah.
2 Chronicles 36:4 And the king of Egypt made Eliakim his brother king over Judah and Jerusalem, and turned his name to Jehoiakim. And Necho took Jehoahaz his brother, and carried him to Egypt.
2 Chronicles 36:5 Jehoiakim was twenty and five years old when he began to reign, and he reigned eleven years in Jerusalem: and he did that which was evil in the sight of the LORD his God.
2 Chronicles 36:6 Against him came up Nebuchadnezzar king of Babylon, and bound him in fetters, to carry him to Babylon.
2 Kings 24:1 In his days Nebuchadnezzar king of Babylon came up, and Jehoiakim became his servant three years: then he turned and rebelled against him.
2 Kings 24:6 So Jehoiakim slept with his fathers: and Jehoiachin his son reigned in his stead.
2 Kings 24:8 Jehoiachin was eighteen years old when he began to reign, and he reigned in Jerusalem three months. And his mother's name was Nehushta, the daughter of Elnathan of Jerusalem.
2 Chronicles 36:8 Now the rest of the acts of Jehoiakim, and his abominations which he did, and that which was found in him, behold, they are written in the book of the kings of Israel and Judah: and Jehoiachin his son reigned in his stead.
2 Chronicles 36:9 Jehoiachin was eight years old when he began to reign, and he reigned three months and ten days in Jerusalem: and he did that which was evil in the sight of the LORD.
Daniel 1:1 In the third year of the reign of Jehoiakim king of Judah came Nebuchadnezzar king of Babylon unto Jerusalem, and besieged it.
Daniel 1:2 And the Lord gave Jehoiakim king of Judah into his hand, with part of the vessels of the house of God: which he carried into the land of Shinar to the house of his god; and he brought the vessels into the treasure house of his god.
Jeremiah 25:1 The word that came to Jeremiah concerning all the people of Judah in the fourth year of Jehoiakim the son of Josiah king of Judah, that was the first year of Nebuchadrezzar king of Babylon;
Jeremiah 25:3 From the thirteenth year of Josiah the son of Amon king of Judah, even unto this day, that is the three and twentieth year, the word of the LORD hath come unto me, and I have spoken unto you, rising early and speaking; but ye have not hearkened.
Jeremiah 46:2 Against Egypt, against the army of Pharaohnecho king of Egypt, which was by the river Euphrates in Carchemish, which Nebuchadrezzar king of Babylon smote in the fourth year of Jehoiakim the son of Josiah king of Judah.
Jeremiah 52:28 This is the people whom Nebuchadrezzar carried away captive: in the seventh year three thousand Jews and three and twenty:
AM 3617 is the beginning of Jehoiakim's Judaic reign, and if we add 4 years, unto the 4th year of his Judaic reign, AM 3617 + 4 = AM 3620/1 (4th year Jehoiakim, 1st year Nebuchadnezzar), which historically becomes the 1st year of Nebuchadnezzar's reign in Babylon.
The Bible says that Nebuchadnezzar, “in the seventh year” (Jer 52:28) he took captives, 3023 Jews. If we consider the context of Jeremiah 52:28-30, this would mean then, that it is the 7th year of Nebuchadnezzar's reign, being AM 3627/8, placing it right at the time of Jehoiakim's captivity.
Jehoiakim, serves Nebuchadnezzar for “three years” (2 Ki 24:1), which is what Daniel refers to (Dan 1:1) as the “the third year of the reign of Jehoiakim king of Judah”. In other words, it was the 3rd year of Jehoiakim's reign being subjected to the greater earthly King of Kings (Dan 2:37), not the third year of Jehoiakim's Judaic reign, but instead Jehoiakim's 9th year of Judaic reign. Jehoiakim after serving Babylon three years (AM 3624/5 - AM 3627), he rebelled, and so Nebuchadnezzar has to come and “besiege” Jerusalem, and in the following months/year, we come to AM 3628, in which Jehoiakim is taken captive (Dan 1:2), deposed and his son Jehoiachin is placed upon the throne in his stead (2 Ki 24:6; 2 Chr 36:8).
AM 3628 – 4 = AM 3624, when Jehoiakim began to serve King Nebuchadnezzar, in which from AM 3624/5 – AM 3627, Jehoiakim, served “three years” (2 Ki 24:1). In this 3rd year (AM 3627) of subjection, Jehoiakim decides to no longer be subject to Nebuchadnezzar, and so rebels (Dan 1:1), and in the 4th year of being subject, or the 11th year of his Judaic reign (AM 3628), he is taken captive by Nebuchadnezzar (Dan 1:2) and eventually dies (2 Ki 24:6).