Q: WHAT YEAR DID HEZEKIAH 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 662 BC.
On the Hebrew calendar, sometimes called the biblical calendar, the year was 3385 AM.
2 Kings 18:1-2 New King James Version (NKJV)
Hezekiah Reigns in Judah
18 Now it came to pass in the third year of Hoshea the son of Elah, king of Israel, that Hezekiah the son of Ahaz, king of Judah, began to reign. 2 He was twenty-five years old when he became king, and he reigned twenty-nine years in Jerusalem. His mother’s name was Abi the daughter of Zechariah.