For a long time it was months. The original BRs say 60 months (ie 5 years) and then moving to 39 months in 2015. That 1185 days you listed wasn't ever actually in a written document, it's how Chromium browsers generously estimate 39 months.

But yes, none of it matters any more. Apple insisted on 398 days, they decided it is a compliance issue, so all legit leaf certificates in the Web PKI that haven't expired have a maximum lifespan of 398 days.

People tend to think about it as a year or two years because the way a for-profit CA used these limits was to sell annual certificates but allow early renewal without losing out. Say you bought a cert on June 10th 2022, this year as the end of May approaches you get an email (In reality use automation, please) saying hey, you should renew soon. You can pay up on 29th of May, you get a new certificate which expires on... June 10th 2024. They couldn't do that if the rules didn't allow enough extra days.