In these charts time interval is a scale parameter. Concepts are described by the relative length of the time interval. This is not historical time.
Historical time runs across the bottom of a graph with the origin at the lower left.
For contrast time as a scale parameter runs across the top of the graph with the origin at the upper left. There are two criteria that guide this reconstruction. One is simplicity. The second is describing implications for models of dynamic social systems. Two charts are defined by scale parameters.