whyizit
The seventy years was a period of servitude, desolation and exile of the Jews deported to Babylon in 607 BCE until they were released from Babylon due to her fall in 539 BCE in the year 537 BCE. Most if not all modern authorities discard any notion or importance of the seventy years and thus use a chronology based on the regnal years of the Babylonian kings counting from 539 BCE which marked the end of the Babylonian Monarchy places the fall of Jerusalem in 587 or 586 BCE.
The difference between secular and Bible chronology is one of methodology and the seventy years, WT chronologists such as the celebrated WT scholars insist that a true biblical chronology must factor in the biblical 'seventy years.'
scholar JW