Need a calendar system

I am looking for a PHP based basic calendar system. Mainly used for employees. I need individual user logins, in where users login, and they are able to type in there hours. They must be able to view a calendar in which displays when they have worked. i will then need there to be an administrator to view all of the employees hours, and see when they have worked. When the employee is logging in there hours it must have the following fields: Name (which should be auto filled, and not able to change) Lunch Duration (.30hours, .45 hours, 1 hour, etc etc.) Start time / End time Fellow employees hours should be hidden from eachother.