thirty years ago, I began to program as a hobby. My greatest programming achievement was simple on the surface of it (above) -- a Church Calendar for MSDOS. It covered 1980-2099, and held near exhaustive information, combining Protestant, Anglican, and Catholic data. In this video, I scroll through the 2017 calendar till Advent this year (3 December), then search for Easter next year (1 April), then check what happens on 25 December this year (Christmas, of course). The calendar was customisable, too. OBSERVATION: A Church calendar follows both the Gregorian and the solar calendars, so one needs (among other things) to calculate the position of the sun, and correlate this with the Gregorian calendar -- in this case over a period of 120 years. Richard Regez of Switzerland helped me with the astronomical algorithms. My original calendar works smoothly. The jerkiness here is due to grabbing it off a DOS window running under Linux. Ultimately I switched to electronics. Programming is too quickly dated.