Time in Quantum mechanics, stands as an unresolved problem from the first time the theory was established to the present day. The present thesis consists of three main studies, in the first part, some time formulas that have been proposed in the past are included. In the second part, time is formulated by using David Bohm's "the guiding equation". In the third part, time formula has been applied to atomic potentials (He, Ar and Kr noble gases) for which time measurements done. It has been shown that the ionization time of the noble gases we have calculated gives results very compatible with the experiments.