ABSTRACT
The BIPM is responsible for the calculation of the Coordinated Universal Time (UTC), its rapid solution, UTCr, and the realization of Terrestrial Time TT(BIPM). UTC is calculated each month, UTCr each week and TT(BIPM) each year.
In this talk I will present the role of Primary and Secondary Frequency Standards (PSFS) in international time scale calculation, focusing on how they guarantee the long term stability and accuracy of UTC. For this purpose, the TT(BIPM) algorithm will be introduced and the latest calculation (2022) of this time scale presented.