  Normally we quantize along the space dimensions but treat time classically.
But from relativity we expect a high level of symmetry between time and space.
What happens if we quantize time using the same rules we use to quantize space?
To do this, we generalize the paths in the Feynman path integral to include
paths that vary in time as well as in space. We use Morlet wavelet
decomposition to ensure convergence and normalization of the path integrals. We
derive the Schr\"odinger equation in four dimensions from the short time limit
of the path integral expression. We verify that we recover standard quantum
theory in the non-relativistic, semi-classical, and long time limits. Quantum
time is an experiment factory: most foundational experiments in quantum
mechanics can be modified in a way that makes them tests of quantum time. We
look at single and double slits in time, scattering by time-varying electric
and magnetic fields, and the Aharonov-Bohm effect in time.
