Then Jehoiachin king of Judah, his mother, his servants, his princes, and his officers went out to the king of Babylon; and the king of Babylon, in the eighth year of his reign, took him prisoner. 2 Kings 24:12 NKJV
According to the Old Testament, the siege of Jerusalem in 597 BCE took place in the 8th year of the reign of Nebuchadnezzar II. The Nebuchadnezzer Chronicle, however, which mentions the same event, dates it in his seventh year
Scholars generally say that this is because the Babylonians/Persians used the "ascension-year" method of dating regnal years, meaning that the first regnal year of a king would begin in the first month the following year he ascended the throne.
To those who are learned in this topic, is there a reason why the Babylonians/Persians reckoned the regnal years of their kings this way?