Third Dimension of Time: Retention

In the common concept of Time, the Present is conceived as leaving the Past behind, even if continuity obtains in between.  In contrast, in the concept of Time as cumulative, the Past is within the Present.  In that case, corresponding to Spatial Depth is the third Dimension of Time: Retention.  Retention is expressed in any process of counting, i. e. because an earlier quantity is included in a later one.  In other words, Measurement entails Time-Retention.  Furthermore, Retention is ingredient in such fundamental Physics concepts as Inertia, Momentum, and Potential Energy.  So, if a Physicist so opted, their concept of 4-Dimensional Space-Time could be extended to 6-, without loss of relevance.