From 8900e1242952df46753f636297682d396644f26a Mon Sep 17 00:00:00 2001
From: Shahram Najm <masn@ecmwf.int>
Date: Thu, 11 Aug 2022 11:16:24 +0100
Subject: [PATCH] Documentation

---
 src/grib_accessor_class_bufr_extract_datetime_subsets.c | 3 ++-
 src/grib_accessor_class_g2end_step.c                    | 2 +-
 src/grib_date.c                                         | 7 +++++--
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/grib_accessor_class_bufr_extract_datetime_subsets.c b/src/grib_accessor_class_bufr_extract_datetime_subsets.c
index 7fdc451ee..2658fce54 100644
--- a/src/grib_accessor_class_bufr_extract_datetime_subsets.c
+++ b/src/grib_accessor_class_bufr_extract_datetime_subsets.c
@@ -157,7 +157,8 @@ static int get_native_type(grib_accessor* a)
 /* Convert input date to Julian number. If date is invalid, return -1 */
 static double date_to_julian(long year, long month, long day, long hour, long minute, double second)
 {
-    double result = 0;
+    double result = 0; /* Julian number in units of days */
+
     /* For validating the date/time, we specify seconds as an integer */
     long lSecond = (long)second;
     grib_datetime_to_julian(year, month, day, hour, minute, lSecond, &result);
diff --git a/src/grib_accessor_class_g2end_step.c b/src/grib_accessor_class_g2end_step.c
index 9ecd541d6..1f69a7a60 100644
--- a/src/grib_accessor_class_g2end_step.c
+++ b/src/grib_accessor_class_g2end_step.c
@@ -561,7 +561,7 @@ static int pack_long(grib_accessor* a, const long* val, size_t* len)
     if (err != GRIB_SUCCESS)
         return err;
 
-    dstep = (((double)(*val)) * u2s[unit]) / u2s[2];
+    dstep = (((double)(*val)) * u2s[unit]) / u2s[2]; /* in days */
     dend += dstep;
 
     err = grib_julian_to_datetime(dend, &year_of_end_of_interval, &month_of_end_of_interval,
diff --git a/src/grib_date.c b/src/grib_date.c
index 0f3cb851c..acb7ca76e 100644
--- a/src/grib_date.c
+++ b/src/grib_date.c
@@ -9,8 +9,11 @@
  */
 
 /***************************************************************************
- *   Enrico Fucile                                                            *
- *                                                                         *
+ * 
+ * The Julian date of any instant is the Julian day number plus the fraction of a day
+ * since the preceding noon in Universal Time.
+ * Julian dates are expressed as a Julian day number with a decimal fraction added.
+ *
  ***************************************************************************/
 #include "grib_api_internal.h"