If server is 5 hour ahead of CST, but you're still taking the time from the server. Why would you need to change the time? What time defines "today" and "yesterday"?
Luis C.
General Disclaimer:
Are you seriously taking the advice and code from someone from the internet without testing it? Do you at least understand it? Or can it easily kill your server?
How to post data/code on a forum to get the best help: Option 1 / Option 2