       Re: Calculating Easter

• To: mathgroup at smc.vnet.net
• Subject: [mg40784] Re: Calculating Easter
• From: wself at msubillings.edu (Will Self)
• Date: Thu, 17 Apr 2003 03:35:32 -0400 (EDT)
• References: <b78ft4\$l1q\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Part of the original message was mysteriously excised (mea probably
culpa):  This comes from the book _Puzzles and Paradoxes_ by T. H.
O'Beirne, Oxford University Press, 1965.  O'Beirne mentions that over
the years various mathematicians have given erroneous formulas,
including Gauss.  Gauss' formula is wrong for the year A.D. 4200 and
certain later years.

wself at msubillings.edu (Will Self) wrote in message news:<b78ft4\$l1q\$1 at smc.vnet.net>...
> An example of the function below is
>
> easter   --->
> In the year 2003, Easter falls on April 20.
>
>
> Press, 1965, page 168:
> "...we shall give a purely numerical rule -- subject to no exceptions
> of any kind -- which calculates the date of Easter from a knowledge
> only of the year number..."
>
> I have retained O'Beirne's same variable names, except that I added
> the variable nn.
>
> easter[year_] :=
>   Module[{x = year, b, c, d, e, g, h, i, k, mu, lambda, n, p, nn},
>     a = Mod[x, 19];
>     b = Quotient[x, 100];
>     c = Mod[x, 100];
>     d = Quotient[b, 4];
>     e = Mod[b, 4];
>     g = Quotient[8b + 13, 25];
>     h = Mod[19a + b - d - g + 15, 30];
>     mu = Quotient[a + 11h, 319];
>     i = Quotient[c, 4];
>     k = Mod[c, 4];
>     lambda = Mod[2e + 2i - k - h + mu + 32, 7];
>     n = Quotient[h - mu + lambda + 90, 25];
>     p = Mod[h - mu + lambda + n + 19, 32];
>     nn = Switch[n, 3, "March ", 4, "April "];
>     Print[
>       "In the year " <> ToString[x] <> ", Easter falls on " <> nn <>
>         ToString[p] <> "."];]

```

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