Local Accrual as the Only Intrinsic Time-Quantity - A Positive Structural Statement for the Massive Regime

For a massive object, the locally accrued proper time along its worldline is the only time-quantity intrinsic to it. Coordinate time, registered dilation, simultaneity assignments, and frame-dependent timestamps are between-frames relations, not intrinsic properties. This paper states that distinction as a positive structural claim. The accrual is the integral of the local clock-tick interval along the worldline; it requires no second frame, no coordinate choice, and no apparatus external to the worldline. Every other time-quantity standardly associated with the object requires such an external reference and is therefore relational. The argument uses only standard relativistic kinematics and introduces no new equations, constants, or postulates. The claim is interpretive: it states which of the time-quantities licensed by the standard formalism are worldline-internal and which are between-frames, and it identifies the locally accrued proper time as the unique member of the first category. The asymmetric outcomes that relativity correctly predicts — different ages at reunion, particle survival across long flight paths, GPS clock offsets — are determined by differences between worldline-internal accruals. Registration relations describe how these worldline-internal facts are reported across frames; they do not produce the facts. The paper is conservative with respect to Special and General Relativity: it states what the formalism already entails about which time-quantities are intrinsic and which are relational.