Q: WHAT YEAR DID AMAZIAH BEGIN HIS REIGN IN JUDAH?
A: IT DEPENDS WHAT CALENDAR YOU ARE USING!
On the Gregorian calendar (the one you might have on your wall) the year was 783 BC.
On the Hebrew calendar, sometimes called the biblical calendar, the year was 3264 AM.
2 Kings 14:1-2 – 1 In the second year of Joash son of Jehoahaz king of Israel reigned Amaziah the son of Joash king of Judah. He was twenty and five years old when he began to reign, and reigned twenty and nine years in Jerusalem. And his mother's name was Jehoaddan of Jerusalem.