[Note: The beginning of a seventy-year period regarding Babylon began with the reign of King Jehoiakim of Judah, and the overthrow of the last declared king of Assyria, Ashur-uballit II of the Neo-Assyrian Empire (2 Kgs. 23:34; Jer. 24:1).
In the year 609 BCE, Pharaoh Necho of Egypt (Nekau II) took his army north to Carchemish in support of the Assyrians in his first military campaign against the Babylonians. This prompted King Josiah of Judah to throw off the Assyrian influence by attempting to halt the Egyptian’s advance at Megiddo. Unfortunately Josiah was wounded and died in late summer of 609 BCE. His son Jehoahaz then reigned for three months and 10 days until he was deposed. Then Jehoiakim (Eliakim) was placed on the throne, beginning his accession year in the fall of 609 BCE.
Thus the resulting defeat and route of the Egyptians at Carchemish in this year brought to a close the final days of the Neo-Assyrian Empire. And it marked the establishment of the Neo-Babylonian domination with the rule of King Nabopolassar and crown prince Nebuchadnezzar in late 609 BCE.
From this starting date we can account for a seventy-year period of time as prophesied by Jeremiah, which ended with the deposing of King Nabonidus and crown prince Belshazzar of Babylon in late 539 BCE (Jer. 25:11). The date for the fall of Babylon is supported by historical records and Daniel’s statement that: “In that night was Belshazzar the king of the Chaldeans slain. And Darius the Median took the kingdom, being about threescore and two years old” (Dan. 5:30-31).
Now even though the starting point for the seventy years is controversial with many dates being offered, the general assumption in accepting some of these dates is based on when the captivity began and ended, or when Cyrus’ decree was announced (Ezra 1:1-5). However, a closer look at Jeremiah’s prophecy shows that a focus for the seventy years prophecy was Babylon, and its impact on the nations of Southwest Asia, Central Asia and the Middle East, including Egypt—meaning that some things prophesied by Jeremiah were related to a seventy-year period, but not counted by it. Thus the people of Judah and Jerusalem did not escape the seventy-year period of Babylonian domination, and the related periods of captivity associated with it.
So in respect to the Babylonian domination we read: ”For thus said Jehovah, Surely at the fullness of Babylon—seventy years—I inspect you, and have established towards you My good word, to bring you back unto this place” (Jer. 29:10, YLT). Another translation states it this way: “For so says Jehovah, When according to My mouth seventy years have been fulfilled for Babylon, I will visit you and confirm My good Word to you, to bring you back to this place” (Jer.29:10).
We can reasonably conclude then that a seventy-year period ended with the fall of Babylon in October of 539 BCE. “And it shall be, when seventy years are fulfilled, I will punish the king of Babylon and that nation, and the land of the Chaldeans, for their iniquity, says Jehovah; and I will make it everlasting ruins” (Jer. 25:12).
Finally then we can say that Babylon was partly at the center of the seventy years prophecy, but the nations, including Judah, would be affected in many different ways and at different times during the seventy years of Babylon’s domination. The result then of these seventy years upon Babylon would initiate other prophecies, such as the destruction upon Jerusalem for seventy years, and the land being granted its Sabbaths for seventy years, which implies there was more than one seventy-year period of time to be accounted for in Jeremiah’s prophecies (2 Chron. 36:20-23).] (andrewburdettewrites.com)