We present a novel temporal framework, the ”applicable time” (𝑡applied), which unifies the effects of cosmic expansion, relativistic dilation, and quantum correc tions to model complex processes, such as the evolution of primordial black holes (PBHs). This framework complements standard temporal metrics (cosmic, proper, coordinate, conformal) by providing a process-specific timescale, ensuring numer ical stability and physical accuracy. The applicable time equations are rigorously derived, including a quantum variant for Planck-scale phenomena. Numerical sim ulations of a PBH with an initial mass of 1012 kg at a redshift 𝑧 = 1089 over 1016 s show a mass reduction to 9.92×1011 kg, an increase in Hawking temperature from 1.22 × 10−3 K to 1.25 × 10−3 K, and a negligible impact on the cosmic microwave background (CMB), with distortions 𝑦 ≈ 1.09×10−23 and Δ𝑥𝑒 ≈ 1.03×10−23, consis tent with Planck 2018 limits Planck2018. Complete Python codes are provided for reproducibility, optimized for Python 3.13.3, addressing all reviewer concerns from Open Astronomy (astro-D-25-00016), including derivation clarity, mass consistency, and framework necessity. This work establishes applicable time as a robust tool for cosmic simulations, with potential applications for CMB-S4.