sw/rescue/lab8e_goettingen/disk2_11/rka/paroff/easter.ft

   1         SUBROUTINE EASTER (YEAR,ESTDAY,ESTMON)
   2 C
   3 C       IN MEMORIAM KARL FRIEDRICH GAUSS
   4 C
   5 C       INPUT PARAMETER
   6 C        YEAR TO COMPUTE THE EASTER DAY 1700 TO 2099
   7         INTEGER YEAR
   8 C       OUTPUT PARAMETER
   9 C        MONTH OF EASTERN 3 OR 4 (MARCH OR APRIL)
  10         INTEGER ESTMON,
  11 C        DAY OF EASTERN RANGES FROM 1 TO 31
  12      *          ESTDAY
  13 C
  14 C        CONSTANTS FOR 17TH, 18TH, 19TH, 20TH CENTURY
  15         INTEGER Y(4),Z(4),
  16      *   R1,R2,R3,R4,R5,TEMP,CNTURY
  17         INTEGER NCOND
  18         EXTERNAL NCOND
  19         DATA Y,Z /22,23,24,24,3,4,5,5/
  20 C
  21 C
  22 C        THE CENTURY WANTED --> CNTURY
  23         CNTURY=YEAR/100-16
  24 C
  25         R1=MOD(YEAR,19)
  26         R2=MOD(YEAR,4)
  27         R3=MOD(YEAR,7)
  28         R4=(R1*19+Y(CNTURY))/30
  29         R5=(2*R2+4*R3+6*R4+Z(CNTURY))/7
  30         TEMP=R4+R5+22
  31 C       TEMP HOLDS EASTER DAY PAST THE FIRST OF MARCH
  32         TEMP=NCOND(TEMP.EQ.56 .AND. R1.GT.10 .AND. R4.EQ.18,TEMP-7,
  33      *   TEMP.GT.56,TEMP-7,TEMP)
  34         ESTMON=NCOND(TEMP.GT.31,4,3)
  35         ESTDAY=NCOND(TEMP.GT.31,TEMP-31,TEMP)
  36         RETURN
  37         END
  38 \1a