A shifting date line - an interesting feature of the solar calendar

The solar calendar, in an internationalized form, has just completed its first 100 years. A close examination shows that the present 'fixed' Date-Line system is an approximation to the cyclic shifting technique of the Solar Date Line which corresponds to the true nature of the solar cycle. The schematic Gregorian arrangement leads to a simple civil system, accurate in the long run, but results in significant departures in 75 percent of the dates in each four-year cycle. This aspect is discussed in the light of a similar phenomenon applicable to the lunar calendars.