Opening Time Limit Check Uses User Time, Not Site Name

On my registration site, several users found a loop hole in the opening time such that they could change their personal user timezone to Australian time and thus register early for an event set to allow registration at 12 noon EST. I

I haven't checked the code but my initial guess is that it is currently using the user's timezone with site time as reference to check on event registration opening time. We need to make this check according to the site/server time, not the timezone converted user time.