If I have the actual file and a Bash shell in Mac or Linux, how can I query the cert file for when it will expire? Not a web site, but actually the certificate file itself, assuming I have the csr, key, pem and chain files.
With openssl
:
openssl x509 -enddate -noout -in file.pem
The output is on the form:
notAfter=Nov 3 22:23:50 2014 GMT
Also see MikeW's answer for how to easily check whether the certificate has expired or not, or whether it will within a certain time period, without having to parse the date above.