The optimal robust disturbance rejection problem plays an important role in feedback control theory. Here, its time-varying version is solved explicitly in terms of duality and operator theory. This research activity aims to develop a novel approach to minimize disturbances in a time-varying environment, leveraging the principles of duality and operator theory. The proposed method will provide a robust and efficient solution to the disturbance minimization problem, enabling the development of advanced control systems that can adapt to changing conditions.