The average human’s lifetime spans ~6 distinct historical eras today, each 12-15y long. So it’s like living through a 6-part movie series.
Historically the average was 1 because lifespans were shorter and history was much slower.
Era boundaries tend to be a rough global consensus within a 2-3 year band so you’ll likely be born in the middle of one and die in the middle of one too.
So 5 full eras and 2 bookend half-eras. Which means cold open part 1, leave before learning how part 7 ends.
I think recent eras are:
1964-1979: long 60s
1980-1993: long 80s
1994-2007: long 90s
2008-2021: long Weirding
2022-2033: long 20s
Enough time has passed that long 80s, long 90s feel like “history” to me now. Don’t remember long 60s since I was only 5 when it ended.
Would suggest that long 60s started and ended a little earlier, like 61-74. The 70s were distinct, but as you’ve correctly decided, not even a decade, much less an era.
I think for the US 61-74 is more appropriate but globally, 64-79 makes more sense. Civil war act and Iran revolution are probably the best global markers.