The universe begins as a singularity of space and time in the form of an hypersphere. At Time Zero gravity would be at its maximum. This means time would be going slow: maximum curvature. But if the universe expanded time would speed up as the gravity of it decreased. The Big Bang might have been slow when you take the gravitational time dimension into account.
The inflation of the universe happened at time zero in order to get the Big Bang over its own gravity.
Gravity is a continuum.