(Comp.sys.hp48)
Item: 2488 by jdg@hpqtdla.sqf.hp.com [James Gentles]
Subj: Calculating Easter
Date: 22 Dec 1992

There follows a HP48 routine to compute Easter. It accepts either the year
or the date in current format. Internally the routine uses European format,
dd.mmyyyy, and then at the end checks current format with flag -42, and
changes accordingly using a small routine to swap day and month D<-->M
(Sorry, I haven't included this small routine, its not a big deal)

[I took the liberty of modifying the end of the program to make it
 work no matter which date format you use.  Unfortunately, this "fix"
 only allows dates between 1989 and 2088.  If you need dates outside
 this range, change the code back to James' original as listed below.
 -jkh-]

The output is the date of Easter in current date format on the stack.

James
------------------cut here  estr ------------------------------------------
%%HP: T(3)A(D)F(.);       
\<<
  IF DUP 100 >
  THEN 1000000 /
  END .01 MOD DUP
1000000 * DUP 19
MOD 19 * 24 + 30
MOD DUP 6 * ROT DUP
4 MOD 2 * SWAP 7
MOD 4 * + + 5 + 7
MOD OVER + \-> d m
  \<<
    IF m 9 \<=
    THEN 22 m + .03 +
    ELSE m 9 - 'm' STO
      IF m 26 ==
      THEN 19.04
      ELSE
        IF m 25 == d 28 == AND
        THEN 18.04
        ELSE m .04 +
        END
      END
    END +
    IF -42 FC?          @ changed these \    DATE RCLF ROT -42
    THEN D\<-\->M       @ lines to this: >   SF \->DATE STOF
    END                 @    -jkh-      /    DATE SWAP \->DATE
  \>>
\>>
------------------cut here  estr ------------------------------------------
       I have no professional connection with Hewlett-Packard's 
     calculator operations other than as a user of their products.
------------------------------------------------------------------------
 Opinions expressed are my own, and are not intended to be an official
           statement by Hewlett-Packard Company/Limited
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  "To strive, to seek, to find, and not to yield."  Ulysses, Tennyson.
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James Gentles     Hewlett Packard,  Amateur: GM4WZP
Queensferry Telecoms Division QTD,    Email: jdg@hpsqf.sqf.hp.com 
Station Road,   South Queensferry,   HPDESK: James Gentles / HP1400 
West Lothian, Scotland,  EH30 9XR.    Phone: +44 31 331 7663, FAX: ~7488
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