Read SSL PEM generated file to get certificate expiry date

Question

I'm using https://github.com/fszlin/certes to generate an SSL PEM file and private key, but throughout the process I can't seem to see where to get the certificates expiry date (or even if it's in there). I have found the order expiry date which is 7 days from now. Does anyone know if it's a property I can extract in some method or maybe later read the PEM to get the data out from there? I know I can get it from the https url once the certificate is installed, or just simply add on 90 days onto the created date, but it would be handy to get it from the certificate itself in some form during the creation process.