Remember, that was back in the hippy free love days. They probably just came up with a year because they needed to fill in a blank without bothering to count back 9 months or didn't care about being full term. Or maybe they claimed common law marriage though from all reports they never really lived together.
Not really. The hippies didn't come forth until a few years later. I lived in Berkeley in 1964. The "summer of love" and the advent of the "hippie" movement was 1967. THings got really bad in Berkeley in 1968 which is when I picked up my family a moved (and registered Republican).
1964 was the beginning of the "free speech movement". Berkeley was still pretty conventional in 1964 which is why Mario Savio's protest against the Regents and Gov. Ronald Reagan was such a shock to the community. Of course Dunham came from a radicalized background at Mercer Island HS, and her parents had Commie connections -- so, perhaps she was avante garde.