What URL / domain are you getting that on? I'm not seeing any certificate error. I just verified the date of 5 different domain/subdomains that contain vgchartz.com names that are good (and another 10 non production ones). Perhaps you are using a deprecated domain alias?
Hmm, that's interesting. I'm still getting it on the main page:
My PC's time also seems to be correct, so it's not that either... It's a Let's Encrypt certificate which says it's valid from Sep 20 until Dec 19 (i.e. when I reported the problem). I can provide more details about the certificate if necessary, but I'm getting the same issue in both Chrome and Firefox, so there's definitely something wrong with the certificate.