Heidegger's Bible Handbook: Ezekiel: Chronology
4. Inquiry is made after the time in which he prophesied. The thirtieth year in Ezekiel 1:1, whether it was from the birth of the Prophet, or the entrance of Nabopolassar?
So that we might say something concerning the time of his Prophecy, he himself testifies in Ezekiel 1:1, 2, that he saw, or began to see, visions in the thirtieth year (which is reckoned from the Jubilee by Father Kimchi, and of our men Calvin: from the finding of the book of the law, and that most famous Paschal feast solemnly celebrated in the eighteenth year of Josiah, by ancient and more recent men not a few, to whom also subscribe of the Hebrews Jonathan the Paraphrast and David Kimchi, and of our men Junius: from the birth of the Prophet, by Gregory and others: from the beginning of the Rule of Nabopolassar, or of Nabuchodonosor the elder, from whose first year a new era was instituted and perpetually observed by the Chaldean Astrologers, by Joseph Scaliger with sufficient probability), in the fourth month, on the fifth day: it is added, this was the fifth year of King Jehoiachin’s captivity. It falls in the midst of the time of the Reign of Zedekiah, in which the state of Judah was peaceful. But he had the final vision in the twenty-fifth year of the captivity, Ezekiel 40:1. Whence it is calculated that he prophesied for twenty years. Now, in what year he began to prophesy, Jeremiah had already passed the thirty-fourth year of his Prophetic office undertaken at Jerusalem, and prophesied together with him at least eight years, with great labor, but not with answerable success.
 Rabbi Joseph Kimhi (1105-1170), father of Moses and David Kimchi, was a French Rabbi. He commented on the entire Hebrew Bible, emphasizing the literal meaning arising from the grammar of the text. Only fragments of his work survive.  2 Chronicles 35:1-19.  Nabopolassar reigned from 626 to 605 BC.