Clock, Watch, and Time Measurement, Calibration and Testing

From cell phone clocks to digital alarm clocks, to expensive gold watches to the clock on their microwave ovens and other appliances, many people in the Unites States were adjusting time monitoring devices today for the US’s Daylight Savings Day.  Along with the public, manufacturers were also calibrating the internal clocks of processors on their manufacturing lines and equipment.  Many products such as Global Positioning System (GPS) satellite receivers, and the electric power grid depend on the accuracy and reliability of their internal clocks. So, how is time measured?

Time is calibrated to atomic clocks.  In the United States, the first atomic clocks were built by NIST in the 1950s from which measurement standards are developed. In 1967, cesium began to be used in the atomic clocks.

Consumer product clocks for the general public’s use are tested to the The U.S. Department of Commerce’s National Institute of Standards and Technology (NIST) IST-F2,  IST-F2. Since 1999, NIST has determined the length of a second by its NINIST-F1 Standard which measures the length of a second by cesium atoms. In 2014, it released the F2 Standard.  To develop this standard, it was measured  to the International Bureau of Weights and Measures (BIPM) in Paris, France.  This International Organization collates data from atomic clocks around the world. While the NIST keeps “civilian” time, the US Navy keeps the official military time standards at its U.S. Naval Observatory .

In addition to testing to the standard, NIST maintains many services for time calibration including an online service to calibrate Internet Time Service which is used to synchronize clocks in computers and other information technology and network devices.

In 2015, Daylight Saving Time (DST) is in effect from March 8, 2015 at 2 a.m. (local time) to November 1, 2015 at 2 a.m. (local time).  Here’s a NIST Time Widget with the current time. According to the NIST website this is for general use purposes  such as the general time, but should not be used for calibration as it only re-synchronizes with NIST every 10 minutes .