Earlier quoted context omitted.
The standard https check has it built-in with the right flags. Use -h or --help to figure it out. (They provide different output)
That would be /usr/lib/nagios/plugins/check_http --ssl -C 30 -H contracts.comcast.com CRITICAL - Certificate expired on 05/08/2012 23:59.
You rock sir. I was on my phone so I couldn't look it up when I wrote the op. Thanks.