A new theory is presented and tested that time itself is the phenomenon that causes the expansion of the universe and that without expansion, time would simply not be. The model of the theory accurately matches observed cosmological luminosity data consequently accurately describing the observed expansion of the universe. The theory implies that the universe exploded outwards within the dimension of time with all particles expanding from this event within a time blast sphere. Each space dimension is wrapped around the time dimension and every object that is gravitationally separate within the time blast-wave will progress on their own time trajectory of time away from time zero. This has the effect that all objects will expand or move apart as the time sphere expands. We observe distant, and therefore historic, objects on a spiral timeline. We have modelled the theory and shown strong agreement with luminosity observations both at low and high redshift without the need for a cosmological constant thus indicating that the universe is not accelerating in its expansion. The model in fact predicts it is decelerating. The theory also predicts that the unperturbed speed of time expansion will impose a limit on the universe in terms of the fastest speed possible and the speed that light must always travel at. With this limit and as no object can ever be stationary in the time dimension, but that faster and heavier objects will expand less, the theory consequently leads us to explain why special and general relativity occur. Gravity can be explained by the clumping of matter into the dimension of time causing a localised slowing of expansion subsequently causing time dilation and thus resulting in an attractive force with other objects. By this theory, black holes are not singularities but are simply dimples on the time blast wave front.