[gtk/gtk-4-4] calendar: Add an explanatory comment

[Matthias Clasen <matthiasc src gnome org>]

commit c0fc8f796bc9195322df3a774adc332ecdd649cf
Author: Niels De Graef <nielsdegraef gmail com>
Date:   Tue Oct 12 19:37:13 2021 +0200

    calendar: Add an explanatory comment
    
    On the magic numbers used to get the abbreviated day names.

 gtk/gtkcalendar.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gtk/gtkcalendar.c b/gtk/gtkcalendar.c
index fe75e7beaf..d24d58fb9c 100644
--- a/gtk/gtkcalendar.c
+++ b/gtk/gtkcalendar.c
@@ -684,7 +684,7 @@ gtk_calendar_init (GtkCalendar *calendar)
     for (i=0; i<7; i++)
       {
 #ifndef G_OS_WIN32
-        tmp_time= (i+3)*86400;
+        tmp_time= (i+3)*86400; /* epoch was a Thursday, so add 3 days for Sunday */
         strftime (buffer, sizeof (buffer), "%a", gmtime (&tmp_time));
         default_abbreviated_dayname[i] = g_locale_to_utf8 (buffer, -1, NULL, NULL, NULL);
 #else