Latest BIPM Circular T Summary ( PDF)

Bulletin Archive

The BIPM Circular T Summary

The BIPM Circular T Summary is provided here so that users can relate measurements reported in other NPL time and frequency bulletins (which are referenced to the UK national time scale) to the global time standard, UTC. The reason for this two stage process is that UTC is a post-processed time scale. Therefore, a continuously operating national time standard has to be used as an approximation to UTC when monitoring radio time signals. In this context, UTC acts as a regular intercomparison system allowing the differences in the national time scales to be quantified. It also provides participating national time scales with traceability to the SI definition of the second through the contribution of primary frequency standards maintained by just a few national standards laboratories.