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During 2003 the IEN-PTB Two-Way Satellite Time and Frequency Transfer (TWSTFT) link was calibrated using a portable reference station. The calibration activity was conducted in the framework of the Galileo System Test Bed Version 1 (GSTB V1), under a contract with Joanneum Research G.m.b.H. (Austria). The calibration constant was determined with an uncertainty lower than 1 ns. Only few months after the calibration, the satellite provider moved the TWSTFT service to a different satellite; this caused changes non-reciprocal delays of the link (Sagnac and earth stations delays) and the calibration constant had to be re-evaluated. A recalculation of the Sagnac delays is presented together with a re-evaluation of earth stations delays with different measurements techniques.

Laboratory sources for standard frequency and time that receive external time signals to control their built-in oscillators are widely used wherever accurate and stable frequency and time, optionally with universal synchronization, are required. We propose a method to obtain traceability of such signals to Coordinated Universal Time (UTC) and particularly to UTC(PTB), its realization by the Physikalisch-Technische Bundesanstalt (PTB). The role of PTB's weekly published Time Service Bulletin is discussed in detail, and the metrological steps for establishing and maintaining traceability are described and uncertainty contributions are stated. Furthermore, we discuss how to possibly meet financial sector regulations according to European MiFID II. A procedure as a component for the assessment to provide accurate time through telecommunication networks using, eg, the Network Time Protocol (NTP) is presented. It checks outputs of an NTP server to validate that its time reference and provided timeof-day information is in accordance with specific requirements.

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