The NIST Internet Time Service,

We will-describe the NIST Network Time Service which provides time and frequency information over the internet. Our first time server is located in Boulder, Colorado, a second backup server is under construction there, and we plan to install a third server on the East Coast later this year. The servers are synchronized to UTCNIST with an uncertainty of about 0.8 ms RMS and they will respond to time requests from any client on the internet in several different formats including the DAYTIME TIME and NTP protocols. The DAYTIME and TIME protocols are the easiest to use and are suitable for providing time to PCs and other small computers. In addition to UTCNIST, the DAYTIME message provides advance notice of leap seconds and of the transitions to and from Daylight Saving Time. The Daylight Saving Time notice is based on the US transition dates of the first Sunday in April and the last one in October. The NTP is a more complex protocol that is suitable for larger machines it is normally run as a demon process in the background and can keep the time of the client to within a few milliseconds of UTC NIST. We will describe the operating principles of various kinds of client software ranging from a simple program that queries the server once and sets the local clock to more complex demon processes such as NTP that continuously correct the time of the local clock based on periodic calibrations.