In the tenth year that Zedekiah was ruling over Judah the Lord spoke to Jeremiah. ¹  That was the same as the eighteenth year of Nebuchadnezzar.

King Nebuchadnezzar of Babylon came against Jerusalem with his whole army and laid siege to it. The siege began in the tenth month of the ninth year that Zedekiah ruled over Judah. ¹ 

King Nebuchadnezzar of Babylon came against Jerusalem with his whole army and set up camp outside it. ¹  They built siege ramps all around it. He arrived on the tenth day of the tenth month in the ninth year that Zedekiah ruled over Judah. ²