In the eighteenth year of Josiah's reign, this Passover was observed.

2 Kings 23:22
No such Passover had been observed from the days of the judges who had governed Israel through all the days of the kings of Israel and Judah.

2 Chronicles 35:18
No such Passover had been observed in Israel since the days of Samuel the prophet. None of the kings of Israel ever observed a Passover like the one that Josiah observed with the priests, the Levites, all Judah, the Israelites who were present, and the people of Jerusalem.

2 Chronicles 35:20
After all this, when Josiah had set the temple in order, Neco king of Egypt marched up to fight at Carchemish by the Euphrates, and Josiah went out to confront him.

In the eighteenth year of the reign of Josiah was this passover kept.