Simple sunset/sunrise algorithm

include/sun.h

@@ -0,0 +1,35 @@
+#pragma once
+
+#include <math.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/time.h>
+#include <time.h>
+
+// See http://edwilliams.org/sunrise_sunset_algorithm.htm
+#define ZENITH_OFFICIAL 90.83
+#define ZENITH_CIVIL 96.0
+#define ZENITH_NAUTICAL 102.0
+#define ZENITH_ASTRONOMICAL 108.0
+
+/* Given the latlong, returns the seconds in the day, in UTC, that the sun rises
+ * on a given year-month-day, or 0 if it never rises.
+ */
+uint32_t calcSunRise(int year, int month, int day, float latitude, float longitude);
+
+/* Given the latlong, returns the seconds in the day, in UTC, that the sun sets
+ * on a given year-month-day, or 0 if it never sets.
+ */
+uint32_t calcSunSet(int year, int month, int day, float latitude, float longitude);
+
+/* Given a month and hemisphere, a sunrise and sunset (output from
+ * calcSun{Rise,Set}()), returns the amount of seconds of the day where
+ * daylight is observed.
+ * 
+ * Is reasonably aware of polar regions (ie permanent day/night). Exception is the
+ * first full day/night, which are truncated to 86400 respectively 0 seconds. This is
+ * only a concern for any latitude > 66.6 or latitude < -66.6.
+ */
+uint32_t calcDaylight(int month, float latitude, uint32_t rise, uint32_t set);