How to Check SSL Certificate Expiration Date using Terminal

There are multiple ways in which we can check the expiration date of an SSL certificate, let's take a look at a few of them.

Know Certificate Expiration Date for a Website SSL

Example:

# openssl s_client -connect code2care.org:443

CONNECTED(00000003)
depth=2 C = US, O = Google Trust Services LLC, CN = GTS Root R1
verify return:1
depth=1 C = US, O = Google Trust Services LLC, CN = GTS CA 1P5
verify return:1
depth=0 CN = code2care.org
verify return:1
---
Certificate chain
 0 s:CN = code2care.org
   i:C = US, O = Google Trust Services LLC, CN = GTS CA 1P5
   a:PKEY: rsaEncryption, 2048 (bit); sigalg: RSA-SHA256
   v:NotBefore: Jul  9 03:53:07 2023 GMT; NotAfter: Oct  7 03:53:06 2023 GMT
 1 s:C = US, O = Google Trust Services LLC, CN = GTS CA 1P5
   i:C = US, O = Google Trust Services LLC, CN = GTS Root R1
   a:PKEY: rsaEncryption, 2048 (bit); sigalg: RSA-SHA256
   v:NotBefore: Aug 13 00:00:42 2020 GMT; NotAfter: Sep 30 00:00:42 2027 GMT
 2 s:C = US, O = Google Trust Services LLC, CN = GTS Root R1
   i:C = BE, O = GlobalSign nv-sa, OU = Root CA, CN = GlobalSign Root CA
   a:PKEY: rsaEncryption, 4096 (bit); sigalg: RSA-SHA256
   v:NotBefore: Jun 19 00:00:42 2020 GMT; NotAfter: Jan 28 00:00:42 2028 GMT
---
root@b9fc21f2fc40:~# 

The expiration date is displayed in the Certificate chain at level 0 with the label NotAfter.

Know SSL Cert Expiration date using .crt file

# openssl x509 -noout -enddate -in code2care_org_certificate.crt

notAfter=Oct 7 03:53:06 2023 GMT