HOW TO GET NIST-TRACEABLE TIME ON YOUR COMPUTER

Many computer applications require accurate timekeeping. Accurate time is required by computer systems that make and record measurements so that the data is timestamped correctly. Plus, accurate time is often needed to synchronize computer networks. This paper describes a number of different ways that you can use to get accurate time that is traceable to NIST on your computer system. This includes receiving time signals by radio, by telephone, or through the Internet. The cost and performance of each technique is also described. You probably know that PC-compatible computers contain a built-in clock. If you’ve ever relied on a PC clock for timekeeping, you probably also know that it isn’t very accurate. Your wristwatch and most of the clocks in your home probably keep better time than the clock in your PC. Of course, most of us aren’t particularly concerned if the clock is off by a few seconds (or even minutes or hours). If we can tell when we made the most recent revision to a file, we’ll probably be satisfied with our PC’s timekeeping ability. Some PC applications, however, require accurate timekeeping (to the nearest second or better). For example, the computers in a financial institution must keep very accurate records of when transactions were completed, for legal or other reasons, Computer system