can I protect the system time?

I have begun using the timeclock function in one of my
software programs for my employees to clock in and out. My
concern is that they can click on the time in the windows
tool bar, change the clock, clock in or out, and then
change the time back and I would have no way of knowing it
or proving it. Can I password protect the clock? If not,
can I monitor any changes that occur?