We introduce Chronon Phase Transition Cosmology (CPTC), a new framework in which the origin of time, spacetime geometry, and cosmic structure emerge from a critical phase transition in a dynamical temporal vector field Φµ(x), called the Chronon field. In CPTC, the Big Bang corresponds to the spontaneous alignment of this field—akin to symmetry breaking in a three-dimensional Ising model—resulting in a preferred foliation of spacetime we identify as the Real Now. The ensuing dynamics of domain walls, causal propagation, and topological defects drive structure formation, gravitational lensing, and large-scale expan sion. Dark matter arises as an inertial effect of residual foliation shear, while dark energy is reinterpreted as tension from long-lived temporal domain boundaries. Unlike ΛCDM, CPTC requires no inflationary phase, no cosmological constant, and no non-baryonic dark matter. The model yields testable predictions for galactic rotation curves, cosmic microwave back ground anomalies, gravitational wave spectra, and the anisotropic distribution of large-scale structure—offering a unified, geometric origin for cosmological phenomena. This framework completes a longstanding goal in theoretical physics: the unification of spacetime, matter, and cosmic expansion through a dynamical, topologically structured field of time.