Monday, October 25, 2004
Moveable feast
I thought that a moveable feast was a picnic lunch or any other portable event that involved food. I didn't realize that the term has a more specific definition. It refers to a date that's not fixed to a particular day of the calendar year but moves in response to the date of Easter. Moveable feasts include Ash Wednesday and Ascension Day.
Ned has an good post about the date repeat rule for Election Day. It's not the first Tuesday in November, it's actually the first Tuesday after the first Monday in November. As a result, Election Day cannot fall on November 1st.
That's a little more complicated than most repeating date calculations but it's simple compared to the Computus for Easter. The calculation is related to vernal equinox and the cycles of the "ecclesiastic" Moon. Fortunately, mathematician Carl Friedrich Gauss defined an algorithm that can directly compute the date. For the range of years 1900-2099 the calculation in Java looks like this:
Ned has an good post about the date repeat rule for Election Day. It's not the first Tuesday in November, it's actually the first Tuesday after the first Monday in November. As a result, Election Day cannot fall on November 1st.
That's a little more complicated than most repeating date calculations but it's simple compared to the Computus for Easter. The calculation is related to vernal equinox and the cycles of the "ecclesiastic" Moon. Fortunately, mathematician Carl Friedrich Gauss defined an algorithm that can directly compute the date. For the range of years 1900-2099 the calculation in Java looks like this:
I wonder if any C&S systems can support algorithmic repeats like this?int a = year % 19;
int b = year % 4;
int c = year % 7;
int d = (19 * a + 24) % 30;
int e = (2 * b + 4 * c + 6 * d + 5) % 7;
int day = 22 + d + e;
String month = "March";
if (day > 31) { month = "April"; day = day - 31; }
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