NTP Clock Sync is a small utility that forces MacOS X to update the date and time prior to the user log in. It helps resolve issues with Active Directory logins caused by incorrect date and time.
Once installed, NTP Clock Sync is launched by the system at the login window. NTP Clock Sync then updates the date and time using the Network Time Server set in System Preferences.
NTP Clock Sync is very useful for Macs that are using Active Directory (AD) for authentication. Since AD requires the date and time to be very close to the AD Servers date and time, any variation in the Macs clock can result in login problems.
These problems are more evident in Macs that also use Boot Camp. When switching back from Windows the date and time can be hours out of sync. And since by default the MacOS only resyncs the date and time once a user has logged in, this causes major problems with AD.