Ori Industries Existing Routing Protocols expect to maintain contemporaneous, end- to-end connected paths across a network. Changes to that connectivity, such as the loss of an adjacent peer, are considered to be exceptional circumstances that must be corrected prior to the resumption of data transmission. Corrections may include attempting to re-establish lost adjacencies and recalculating or rediscovering a functional topology. However, there are a growing number of use-cases where changes to the routing topology are an expected part of network operations. In these cases the pre-planned loss and restoration of an adjacency, or formation of an alternate adjacency, should be seen as a non- disruptive event. This document attempts to describe the problems perceived with existing routing protocols and act as a "Problem Statement" to be addressed by the proposed Time-Variant Routing (TVR) working group. Readers are recommended to read this document alongside the TVR (Time-Variant Routing) Use Cases (https://datatracker.ietf.org/doc/ draft-birrane-tvr-use-cases/).