Recently it was shown for continuous and discrete-time stationary linear systems that the output stabilizability property of systems can be used to realize ‘almost–positive–rear configurations that may facilitate the implementation of simple, stable, adaptive, and other non–linear controllers. This paper attempts to extend these concepts to time–varying linear systems. It is shown that systems that can be stabilized via static or dynamic output feedback become ’almost–passive‘ via some corresponding parallel feedforward. The proof of the robust stability of simple adaptive control of non–stationary almost–passive systems is also presented.