Dear Calendar People:
I updated the Solar Year Range chart again, now the longest / shortest solar year curves are tangent to the helical curves depicting the mean equinoctial and solstitial years. The only thing I changed is averaging over +/- 1000 years instead of +/- 100 years. The resultant array of points (plotted at 200-year intervals) was almost smooth enough to plot by simply connecting the points, but anyhow I retained the slightly smoother 3rd order polynomial curves.
I also added some introductory discussion below the graph:
-- Irv Bromberg, Toronto, Canada