show how to get a cert's expiry date in certfp.md (#474)

diff --git a/content/kb/using/certfp.md b/content/kb/using/certfp.md
index 7a96e1b0bab894fff8e8dd0baa3a179b4d0c53c5..496d25f9c592cd21717b0db8317cc23d458e9d67 100644 (file)
--- a/content/kb/using/certfp.md
+++ b/content/kb/using/certfp.md
@@ -20,8 +20,10 @@ You can generate a certificate with the following command:
 
 You will be prompted for various pieces of information about the certificate.
 The contents do not matter for our purposes, but `openssl` needs at least one of
-them to be non-empty. This certificate will last about 3 years - set a calendar
-event now to ensure that you are reminded when you need to generate a new one.
+them to be non-empty. This certificate will last about 3 years - you can check the
+expiration date with the following command and set a calendar reminder:
+
+    openssl x509 -in freenode.pem -noout -enddate
 
 The `.pem` file will have the same access to your NickServ account as your
 password does, so take appropriate care in securing it.