source: buchla-68k/orig/DATE/JDAY.C@ 0170798

Last change on this file since 0170798 was 3ae31e9, checked in by Thomas Lopatic <thomas@…>, 7 years ago

Imported original source code.

  • Property mode set to 100755
File size: 1.1 KB
RevLine 
[3ae31e9]1/*
2 =============================================================================
3 jday.c -- convert date to Julian day. -- ACM algorithm 199
4
5 A Julian day is the number of days since some base date
6 in the very distant past.
7
8 Handy for getting date of x number of days after a given Julian date
9 Use jdate() to get that from the Gregorian date.
10
11 Written by: Robert G. Tantzen
12
13 Translated to C by: Nat Howard
14
15 Revised by: D.N. Lynx Crowe
16 1998-01-14 -- optimized for speed
17
18 Translated from the algol original in Collected Algorithms of the <ACM
19 This and jdate() are algorithm 199.
20 =============================================================================
21*/
22
23long
24jday(mon, day, year)
25int mon, day, year;
26{
27 register long y = year;
28 register long m = mon;
29 register long j;
30 register long ya;
31 register long c;
32 long d = day;
33
34 if(m > 2) {
35
36 m -= 3L;
37
38 } else {
39
40 m += 9L;
41 --y;
42 }
43
44 c = y / 100L;
45 ya = y - (100L * c);
46
47 j = (146097L * c) / 4L
48 + (1461L * ya) / 4L
49 + (153L * m + 2L) / 5L
50 + d + 1721119L;
51
52 return(j);
53}
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