I'm currently reading the "Return of the gods". He does provide some very good insight about the influence of these principalities upon society.
I'm reading it because my dad recommended it.
I've seen some of his talks about jubilees. I see he places one around 1917 and one at 1967. But he also talks about shemitahs, so maybe some of the other dates he involves are shemitah years.
I think he is probably running with errors due to the zionist doctrines that have been injected into his eschatology.