How to check the SSL cert expiration date using command?

Answer:

To check the SSL cert expiration date of a domain, you can use the following command:

# echo | openssl s_client -connect www.google.com:443 2>/dev/null | openssl x509 -noout -dates
notBefore=Dec 11 12:02:58 2013 GMT
notAfter=Apr 10 00:00:00 2014 GMT