In this context, we have introduced a clock which link time to temperature by introducing the behaviour of a black body . Our approach is based on the concepts of entropy, energy and interaction (fluxes): these quantities are well defined in any position of the Universe. Moreover, we have also introduced the hypothesis of local equilibrium in order to define temperature . We consider the photons with a well-defined frequency emitted by a black body, in a given rest mass and referred to a temperature scale. In this way, the oscillation frequency is completely linked to the temperature by the analytical relation of dissipation in quantum system . Our results agree with the thermal time hypothesis which states that a preferential time doesn't exist in nature because there are no equilibrium states preferred a priori. We have also introduced the definition of time by using the irreversibility, expressed by the non-negative entropy generation, so that the arrow of time is part of the time physical definition itself. We consider that the Universe is in a continuous non-equilibrium state , but we introduce the hypothesis that in any position it is possible to realise a local thermodynamic equilibrium, such that we can introduce the definition of temperature T [K] in a statistical way as :