This work develops a unified formulation of Extended Classical Mechanics (ECM) structured into three interconnected domains: Dynamics, Geometry, and Cosmology. At its foundation, ECM introduces the accumulated phase variable x° ∈ [0°, ∞) as the primary descriptor of physical evolution, replacing conventional cyclic phase representations with a continuously evolving structural quantity. A central refinement introduced in this formulation is the distinction between phase kernel and phase shift. While phase shift is treated as a universal descriptor of relative phase evolution across both mechanical and electromagnetic systems, the phase kernel is restricted exclusively to mass-based, bounded oscillatory systems, where phase emerges as an intrinsic state variable governed by cyclic energy exchange. To ensure representational consistency across all regimes, ECM introduces a unified degree-based mapping: θᴇᴄᴍ = x° where accumulated phase x° is directly expressed as the ECM phase variable θᴇᴄᴍ, enabling a consistent interpretation of phase accumulation across both kernel and shift domains. In the Dynamics Framework (Part I), physical evolution is governed by monotonic phase accumulation, where classical oscillatory behavior emerges as a projection of x° rather than an intrinsic periodic process. In the Geometry Framework (Part II), wavelength λ, frequency f, and phase velocity Vᴘ are derived as structural manifestations of accumulated phase, establishing λ(x°) as the measurable spatial outcome of phase completion and f(x°) as its temporal density function. In the Cosmology Framework (Part III), ECM extends phase dynamics to universal scales, interpreting redshift, large-scale structure formation, and wave propagation as consequences of spatial gradients in accumulated phase x°(x,t). This replaces purely geometric expansion-based interpretations with a phase transport mechanism governing cosmological evolution. Frequency (f) continues to determine electromagnetic energy through E = hf, while wavelength λ(x°) provides the measurable spatial manifestation of phase structure and governs phase and frequency velocities. The integration of these three frameworks under the ECM Master Phase Transition establishes a coherent, hierarchical, and experimentally interpretable model of wave dynamics and cosmological evolution grounded in accumulated phase physics.