The four-colored diagonal stripes in the previous screen represent the generational bands identified by William Strauss and Neil Howe in their 1991 book, Generations: The History of America's Future, 1584 to 2069.  The y-axis in the chart shows the age of the generational cohort at the date on the x-axis. 

In this important volume of strong historical analysis, Strauss and Howe show how the cycles of American history alternate between periods of Secular Crisis and Spiritual Awakening. And how, as these waves roll through history, each generation is colored by its placement on the curve of the wave. They build their case upon substantial data and then apply its lessons with projections of and recommendations for the future.