Public NTP Time Servers
USNO NTP NETWORK TIME SERVERS
To change internet time synchronization schedule, open your registry and find or create the SpecialPollInterval key located here:
Create or modify "SpecialPollInterval" as a DWORD DECIMAL based key in seconds.
Here are a few common intervals:
Twice a Day=43200
Exit your registry, you may need to restart or log out of Windows for the change to take effect.
This portion contributed by jazzman916