[DBCJR]

So, if 70 symbolizes completion rather than a specific number of years, how did Daniel recognize it was time for the fulfillment of the prophecy?

[WhatNot]

We know from Jer 25:11, 12 and 29:10-14, the desolation of Jerusalm would be fulfilled in seventy years. Daniel's own captivity ocurred in 605 B.C, It was now 538 B.C, some 67 years after the conquest. Daniel recognized the period of captivity was almost over.

Zechariah refers to the seventy year period as begining with the destruction of the temple,which took place in 586 B.C (Zech 7:5). The temple was rebuilt in 515 B.C (Ezra 6:15).

This is why I believe the seventy years has several beginings and endings.