The author of the book pegs Revelation (& the other NT books) as being written before 70 A.D.
Very extensively researched.
His commitment to false theology demanded he reason it so...
"Robinson was considered a major force in shaping liberal Christian theology. Along with Harvard theologian Harvey Cox, he spearheaded the field of secular theology and, like William Barclay, he was a believer in universal salvation.[4]"
From his Wikipedia biography.