  The Heisenberg and Mandelstam-Tamm time-energy uncertainty relations are
analyzed. The conlusion resulting from this analysis is that within the Quantum
Mechanics of Schr\"{o}dinger and von Neumann, the status of these relations can
not be considered as the same as the status of the position-momentum
uncertainty relations, which are rigorous. The conclusion is that the
time--energy uncertainty relations can not be considered as universally valid.
