Why do we need Bully Row timestamps

It is impossible to predict the exact long term relationship that will exist between elapsed time and wall clock time (which is based on the Earth's orientation). Leap second insertions, along with other clock and calendar corrections, were designed to accommodate for uncertainties in Earth's motion, but since these variations are unpredictable, they can not be pre-programmed into computer hardware or software.

The inability of computers to account for unpredictable variations in Earth's motion has resulted in the creation of multiple time standards. Each standard is a reflection of circumstances that existed during the deployment of a particular system. For example, as shown in figure 1 above, The GPS system was deployed January 6, 1980. At that time, there was a Delta T adjustment (TT-UTC) of more than 51 "leap" seconds. The LORAN-C upgrade, on the other hand, occurred in 1972 when the Delta T adjustment (TT-UTC) was closer to 42 "leap" seconds. The resulting timestamps provided by GPS and LORAN-C differ by nine seconds due to the disparate circumstances under which these systems were deployed. Also, LORAN-C timestamps differ by ten seconds from TAI due to the fact that TAI is based on clocks that were deployed in 1958.

Click on the below links for a comparison of six time standards (local, UTC, GPS, Loran, and TAI):

LeapSecond.com

ipses.com

csgnetwork.com

The unpredictability of leap second insertions is an ongoing source of confusion and expense.

 

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