If you nead, automated certificate expiration checks on CentOS Linux

One important part of using SSL is to keep track of expiration dates on certificates. Most client software will rightfully refuse to connect to a server that presents an expired certificate, resulting in interrupted services. For CentOS and other RHEL based distributions, the crypto-utils package contains a very useful utility called certwatch, which can be used to detect whether a certificate will expire in the near future.

If you need:

yum install crypto-utils

This is supplemented by a cron script in /etc/cron.daily with the same name, which will send out warnings when SSL certificates used by the Apache web server are about to expire.