I used MS Word 2003 to do create the flowcharts needed to determine when a year is a leap year for the Gregorian Calendar and the proposed Alternative Calendar. There is one step less for deciding in the Alternative Calendar which shows that this calendar is simpler. At the decision points in the flowcharts the "mod" used is the modulo operator.
The Gregorian Calendar was introduced in late 1582. It was noticed that the Vernal Equinox was shifting relative to the Julian Calendar so a new calendar was devised. This was just prior to the year 1600 which was the last year of the 399th quadrennium, the four year leap year cycle. It was a convenient time to initiate the centennial leap year cycle.
There were other factors that were taken into consideration is developing the Gregorian Calendar. For example the number of days in the 400 year cycle of the calendar is exactly divisible by 7 and the cycle of the weeks will then repeat itself. The Alternative Calendar ignores lunar cycles but it may be possible do something similar for the Lunar Calendar and develop a simple set of rules for it too.
Edit: Corrected the errors involving the year in the Gregorian Calendar Flowchart
Supplemental: The procedure for the Alternative Calendar can be simplified by working in the new system and noting that 2048 is exactly divided by 128. See next blog.