It's been a while since we chatted.
No chronologist says that 539 BCE is an Absolute Date. If it were an Absolute Date, why did Russell and Rutherford use 538 BCE? When and why did the WTS change?
There is NO universal agreement on the date when the first of the Exiles returned. Dates range from 538 to 535 BCE.
The Bible writers do not say that the Exile's Return marked the end of a 70-year period. 2 Chronicles 36, written 200 years later, mentions the 70 years in terms of Cyrus defeating Babylon (see verses 20 and 22). Jeremiah spoke only of several nations serving Babylon for 70 years, not just Judah, and the nations served Babylon while remaining in their own land. Jeremiah told the people they had to continue living in Babylon because their 70 years had yet to continue running its course.
Even though Jeremiah decreed 70 years of servitude to Babylon, he pleaded with the king to accept the situation, so that Jerusalem did not need to be destroyed.
We must not impose 21st century mathematical attitudes upon their ancient cultural attitudes. The number 70 had a cultural meaning.
You are one of the few people who knows that the WTS does not start their "70 years" with Jerusalem's destruction.
As I wrote, I am genuinely pleased to "see" you again.