Fisherman: Compare Jeremiah 29:10 with Isaiah 50:1.
Seems like you are throwing up random Bible verse to distract and obfuscate. Jeremiah 29:10 is part of a letter if instruction from Jehovah to ex-King Jeconiah and his entourage who were captive in Babylon. So it is a letter:
(a) on how to survive the 70 years of captivity, even though according to Watchtower theology they were not part of that captivity;
(b) at a time when, according to Watchtower theology, there was no captivity; and
(c) couriered by a person who was supposed to be dead (according to Watchtower) by the time captivity commenced.
Isaiah 50:1 is prophetic, the Jews not in exile yet. Your referenced scripture is about the completion of 70 and does not establish its start, and its interpretation must also reconcile with 539-70.
Isaiah 50:1 is so vague and nebulous, I can't see how it adds anything. No mention of 70 years, exile, start, finish or anything relevant. Nothing to reconcile there.
Your belief depends upon interpretation but 607 depends upon 539. So unless you can debunk 539, 607 makes sense to me.
Nobody seeks to debunk 539 BC. Everyone agrees that that is the correct date. The point is, 539 BC is NOT 536 BC, a number that would have fitted well with Balbour's milllerite numerology, and fitted with Russell's "pyramid inches".
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There is a simple solution to all of this. The 70 years commenced when the bible says it commenced (see Jer 27:1-6), not when Watchtower® says it commenced.