Check HTTPS Certificate Addon for Confluence
If you are a system administrator with a number of cites under your management, use 'Cert Validity' macro to print expiration date and time of your SSL certificates. Just specify a host address (and optionally a port number) and the macro will automatically print the server certificate expiration date.
Please check the product homepage: http://mesilat.com/FAP/CheckHTTPS
Download from Atlassian Marketplace: https://marketplace.atlassian.com/plugins/com.mesilat.check-https-cert