Demetrios Matsakis, Masterclock, Inc.

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The systematic (Type B) uncertainties in the difference between Coordinated Universal Time (UTC) and the UTC realizations UTC(k) is presented in the context of which time-transfer uncertainties are to be considered. The International Bureau of Weights and Measures (BIPM) currently utilizes only the time-transfer uncertainties of the measurements at the epoch of the computation, and ignores the uncertainties of past time-transfer data despite the covariances between epochs. Algorithms considering all the uncertainties in the initialization and time-transfer yield extremely high and unbounded uncertainties in UTC-UTC(k). A semi-historical algorithm that considers the uncertainty of the extant time-transfer links over all their epochs of validity yields ns-level results, but requires that the history of the UTC-network be taken into consideration. Since this network has matured through re-calibration, the history is limited to determining which UTC(k) are affected when the pivot lab’s GPS system is recalibrated, provided the clock predictions of all labs not linked by GPS are adjusted whenever the pivot lab’s GPS receiver is recalibrated. A way to incorporate redundant links is pointed to.