The NIST Internet Time Service allows users to synchronize computer clocks via the Internet. The time information provided by the service is directly traceable to UTC(NIST). The service responds to time requests from any Internet client in several formats including the DAYTIME, TIME, and NTP protocols.

Absolute Time Corrector (ATC) queries NIST timeservers using the Internet and then compares NIST time to the time setting of the host computer. If there is a disparity, ATC automatically adjusts the computer's time to reflect NIST time.

Once set up the host computer can serve as a timeserver to any size network. The host can be set to check NIST time as often or seldom as desired, and each computer in the network can likewise be set to check time on the host computer as often as deemed necessary by the network administrator.

ATC uses RFC-868 time protocol. This protocol returns a 32-bit unformatted binary number that represents the time in UTC seconds since January 1, 1900. The server listens for Time Protocol requests on port 37, and responds in either tcp/ip or udp/ip formats.