star-cem

commit 450b65536509b53738bde76bab0cca845756a721
parent a325dba13f4afdcb5707263faee14111626d943a
Author: Vincent Forest <vincent.forest@meso-star.com>
Date:   Wed,  8 Oct 2025 12:46:48 +0200

Fix of the Julian date calculation in the Meeus algorithm

It now gives the same result as its PSA variant.

Diffstat:
M
src/scem_meeus.c
 | 
6
+++---

1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/src/scem_meeus.c b/src/scem_meeus.c
@@ -39,10 +39,10 @@ julian_day(const struct tm* time) /* In UTC */
     + (double)time->tm_hour/24.0
     + (double)time->tm_min/1440.0
     + (double)time->tm_sec/86400.0;
-  m = time->tm_mon + 1; /* The months start at 0 */
+  m = time->tm_mon + 1; /* tm_mon start at 0 */
   y = time->tm_year + 1900; /* tm_year is relative to year 1900 (see tm(3type)) */
 
-  if((unsigned)time->tm_mon < 3) {
+  if(m < 3) {
     y -= 1;
     m += 12;
   }
@@ -51,7 +51,7 @@ julian_day(const struct tm* time) /* In UTC */
   b = 2 - a + a/4;
 
   /* Found in "Astronomical Algorithms" by Jean Meeus */
-  jd = (int)(365.25  * (double)(y+4715))
+  jd = (int)(365.25  * (double)(y+4716))
      + (int)(30.6001 * (double)(m+1))
      + d + b - 1524.5;