As probably most of you know, the Nagios plugin check_http can also be used to verify the validity (from the expiration date point of view) of a ssl certificate.
However if you use SNI (multiple SSL certificates on the same IP address), you have to keep in mind to use the --sni switch. Otherwise a wrong ssl certitificate could be shown:
./check_http -H test2.example.com -S -C 30,14
OK - Certificate 'test1.example.com' will expire on 12/23/2014 13:40.
Note the wrong certificate common name.
For SNI enabled web servers, the switch --sni is a must:
./check_http -H test2.example.com -S --sni -C 30,14
OK - Certificate 'test2.example.com' will expire on 12/23/2014 13:42.