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