Albert Barnes Commentary 2 Chronicles 35:20

"After all this, when Josiah had prepared the temple, Neco king of Egypt went up to fight against Carchemish by the Euphrates: and Josiah went out against him." — 2 Chronicles 35:20 (ASV)

After all this - that is, 13 years after, 608 B.C. See the 2 Kings 23:28–29 notes.