Results of macroscopic experiments on the inelastic deformation behavior of solid polymers are used to establish general properties. They include nonlinear rate sensitivity in the inelastic range in monotonic loading and the transition from primary, to primary and secondary, and to primary and secondary and tertiary creep as the creep stress level increases beyond the quasilinear region. Consistent with the notion of a solid it is presumed that a nonzero stress can be sustained at rest. The rest stresses at which relaxation tests terminate form the relaxation boundary. It is suggested that this relaxation boundary has the appearance of a nonlinear stress–strain curve. These properties are used as criteria in evaluating some types of “clock” models where ordinary time in the kernels of linear viscoelastic integral representations is replaced by a transformed time. It is a function of either the invariants of strain or the invariants of stress. It is shown that these models cannot reproduce the change in the creep properties as stress level increases. Creep always terminates. For large times asymptotic solutions hold linear rate sensitivity and a linear relaxation boundary are predicted. Nonlinear rate sensitivity can be modeled before the asymptotic solution is reached.