If you ever want to quickly check the expiration date on your HTTPS server’s SSL certificate all you need is OpenSSL , luckily most of your Linux and OSX workstations will already have it installed.
openssl s_client -showcerts -connect **domain.com**:443 </dev/null 2>/dev/null \
| openssl x509 -noout -dates
You should get back a nice and tidy response with a notBefore and a notAfter date:
notBefore=Mar 13 00:00:00 2015 GMT
notAfter=Mar 12 23:59:59 2018 GMT