i highly doubt Kaido became known as an emperor around 6+ years ago. For all we know, he might be recognized after he successfully conquered Wano 20 years ago.
Novel Ace Vol 2 didn't state that Shanks and Kaido came from same generation, but from younger generation than WB and BM. And this is valid because 38 years ago, Kaido was only starting his career as an apprentice, while WB n Mama already were top pirates in the Rocks. Shanks was an infant back then. I think Kaido is in the same generation as Dragon, Akainu, Moria, Kizaru, Aokiji. While Shanks is with Mihawk, Croco, and Marco. Not saying that age is the only factor, but Kaido did in fact started his career around a decade or so before Shanks.
Akainu dragon kaido Shamks Mihawk are all in middle Generation
It doesn't matter if Kaido started his big run a decade before Shanks. We could deduct kaido became a big name 15-18 years after Golden era ended. Coz Seizeing wano seems like one of his biggest accomplishments.
We know Brook is from an older generation than Roger and co
Since roger was a mere rookie when Brook was alive.
They can exceptions like worstgen who are 40s or 30s yet from luffy Generation coz they started their solo and big run only 2 years ago.
Brook Era lasted probably 10-15 years (roger was a rookie 50 years ago)
Rocks era lasted probably 10-15 years
Golden or "Roger" Era lasted 14 years (till roger death)
"WB" Era lasted 22 years (till wb death)
Worst Gen era started 2 years ago
* Brook generation/Rocks Era
Had big names as Kong /Streussen/Xebec
* almost everyone in Golden era is around 60-79 y.o
Roger Garp WB shiki BM Sengoku Tsuru Zephyr...
* most Middile Gen are 30+ , they all around 30-59 y.o: Akainu Kaido Dragon Doffy Moriah Hancock Shanks Mihawk...
*worst gen fighters are 18+ ,most are in 20s