SSL certificates expire. It’s a fact of life in the world of encrypting communications to web sites. IF you are hitting this same issue, then yes, the correct fix is to install updated CA certificates, and the same problem did affect other browsers. Chrom*-based browsers (including Google Chrome) rely on the operating system’s certificate store. Firefox has its own, which would also have had issues, except Firefox updates (instead of OS updates) deliver new ones when required.
There is a very targeted resolution here: NET::ERR_CERT_DATE_INVALID Error on All Sites - #26 by Barnycc
This all assumes you are having the same underlying problem as others in that thread. If you temporarily disable Avast and try one of the sites again (such as this one) you should more clearly be able to see if it’s the same problem. If it is, then you have the answer above. If it isn’t, then we can start from there when we know Avast isn’t masking the underlying issue.