Automatic Session Logout

For our existing application we want to add the following functionality: 1) All users should be automatically logged out of the application at 2 specific times each day. Once the users are logged out automatically they can then log back into the application. Our time zone is Eastern Standard Time (EST) and the server's time is Central Standard Time (CST) which is 1 hour earlier than EST. 2) This feature should be simple and should not put any strain on the server.