Narkissos
Remember you heard this first from the said scholar that the seventy years are the foundation for the latter 'seventy weeks of years' prophecy. The reasons why this is the case is as follows:
1. Both are prophetic in nature, the latter is given in answer to the prayer about the former.
2. The literary structure of the narrative that is ch.9.
3. The prophecy of verses 24-27 begins with a time element instead of ending with it as is more common with other Danielic prophecies.
4. Common use of the number 70
5. Both are multiples of seven
6. Furthermore, when the symbolic units of the seventy weeks are interpreted according to the literal units of the 70 years, a relationship is produced which parallels the relationship between the jubilee period and sabbactical year period.
7. Such relationship was recognized also by the Qumran community
scholar JW
2.