Time as a Phase-Based Physical Coherence Structure An Ontological Constraint from Exclusion-Based Analysis

Time is universally used in physics, yet its ontological status remains unclear. Classical mechanics treats time as an absolute parameter, relativity embeds it as a spacetime coordinate, and quantum theory typically retains it as an external parameter. This work does not propose a new dynamical theory of time. Instead, it establishes an ontological constraint derived from exclusion-based analysis. The central question addressed is under what physical conditions it is justified to treat a structure as time at all. Through systematic destruction of ordering via permutation, index shuffling, sign inversion, scale variation, and directional reversal, no globally stable classical time structure is found to persist. This negative result is interpreted not as a failure, but as an informative constraint. A physically real but pre-temporal coherence layer, referred to as the Z-level, is identified as the residual structure that remains once all operational notions of time are excluded. Time is shown to emerge only above this level as a directed, stable coherence structure arising from phase differences between periodic and quasi-periodic physical processes. The framework explicitly distinguishes three descriptive levels of time (t₁ ontological, t₂ operational, t₃ historical), clarifying that these are not additional dimensions but levels of description. The results exclude biological and cognitive origins of time and render time travel ontologically undefined rather than technologically forbidden. This work does not invalidate existing physical theories, but clarifies the conditions under which time functions as a meaningful physical concept.