$ sudo openssl x509 -dates -noout -in /etc/letsencrypt/live/[DOMAIN]/cert.pem
# output notBefore=Jun 17 22:38:07 2020 GMT notAfter=Sep 15 22:38:07 2020 GMT
$ sudo openssl x509 -dates -noout -in /etc/letsencrypt/live/[DOMAIN]/cert.pem
# output notBefore=Jun 17 22:38:07 2020 GMT notAfter=Sep 15 22:38:07 2020 GMT