An analysis of the causes, the application of the concept of time, an abstract essence. The reasons for the complexity of determining the movement of time are considered. To determine the essence of time, the process of time movement is considered from the point of view of the internal and external observer. The conclusion is drawn about the movement of time, the transformation of the future into the past. The period of transformation is recorded as the existence of the present. The sum of the transformation periods is recorded as the duration of the event. The property of time periodicity allows measuring its duration using various periodic phenomena and their sums. Continuity of transformation creates the continuity of the movement of time. The conditions of the transformation are considered, one of which is the existence of 3-dimensional space. An analysis is made of the causes, the probabilistic nature of events, in quantum mechanics.Keywords: time, space, matter, transformation, dimensionality of space, quantum uncertainty, cosmology.