All of a sudden on Sept. 30, I can't access a bunch of different sites on my El Capitan Mac Pro, in Chrome and Safari, but Firefox works.
I get this error in Chrome:
Your connection is not private
Attackers might be trying to steal your information from variety.com (for example, passwords, messages, or credit cards). Learn more
NET::ERR_CERT_DATE_INVALID
In Safari, I get this error:
Safari can't verify the identity of the website "variety.com".
The certificate for this website is invalid. You might be connecting to a website that is pretending to be "variety.com", which could put your confidential information at risk. Would you like to connect the website anyway?
Note that I emptied the cache in Chrome, and even reinstalled it to no avail. Then I took the nuclear option and reinstalled El Capitan, swapped RAM, and even swapped to a different Mac Pro and still get the same result. I tried switching DNS servers but that doesn't help either. Ethernet and WiFi are also the same result.
Works fine on my iMac 2017 with Big Sur.
Note that this happened around the same time my first Mac Pro became unstable, due to bad RAM, but like I said I reinstalled El Capitan and swapped out the RAM, and even used a different Mac Pro, but the results are the same. (The current Mac Pro is completely stable on 10.11.6. Both Mac Pros are 1,1 flashed to 2,1.)