Last I looked on some older machines, a ton of certificates for browsers and code signing also expire Jan 1 2020. I've always wondered about this, whether 'tis better that they expire all on the same date, or if expiration should be spread out.
If they all expire at the same time, then diagnosing why a computer suddenly failed is a lot easier. Once you figure out why one failed, that'll be a top thing you'll look for when diagnosing other failures. When spread out, it'll be a surprise every single time.
On the other hand, when certificates all expire at once, you get Y2k situations where the cost of failures gets amplified. Instead of small outages quickly dealt with, you have a cascade of failures.
Maybe we should have a standard, such as certificates expire only on the 15th of every month, or systems allowing until the next 15th before rejecting them. Thus, they clump up well enough we can identify these failures, but not so much they cause catastrophe.
I work a lot with older systems. It's AMAZING how hard it is to keep legacy computers running, because the moment certificates expire, they can no longer connect to the Internet.
