Linux/SSL

Check certificate expiration:

openssl x509 -text -noout -in cert.crt
       Validity
           Not Before: May 10 19:02:45 2023 GMT
           Not After : May  7 19:02:45 2033 GMT

Check website certificate:

openssl s_client -connect google.com:443 | openssl x509 -noout -dates
  notBefore=May 19 12:53:06 2023 GMT
  notAfter=Aug 11 12:53:05 2023 GMT

ref: [1]