From 1363655b59da6a8e87e64f54bb61522dfa70a7b3 Mon Sep 17 00:00:00 2001
From: Steffen Vogel <post@steffenvogel.de>
Date: Fri, 3 May 2013 18:27:33 +0200
Subject: [PATCH] fixed issue with timezone and dst handling on openwrt
 platforms, thx !gm

---
 src/sun_main.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/src/sun_main.c b/src/sun_main.c
index 2a67a54..f7707ab 100644
--- a/src/sun_main.c
+++ b/src/sun_main.c
@@ -25,6 +25,8 @@
  * along with sun. If not, see <http://www.gnu.org/licenses/>.
  */
 
+#define _BSD_SOURCE 1 /* for tm_gmtoff field in struct tm */
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdbool.h>
@@ -32,7 +34,8 @@
 #include <getopt.h>
 #include <float.h>
 #include <math.h>
-#include <sys/time.h>
+#include <time.h>
+#include <limits.h>
 
 #include "../config.h"
 #include "sun.h"
@@ -120,7 +123,7 @@ int main(int argc, char *argv[]) {
 	char *format = "%H:%M";
 	char *query = NULL;
 	bool error = false;
-	int timezone = 0;
+	int timezone = INT_MAX; /* magic value for system default with dst */
 
 	enum mode mode = INVALID;
 	struct tm date;
@@ -131,12 +134,6 @@ int main(int argc, char *argv[]) {
 	time(&t);
 	localtime_r(&t, &date);
 
-	/* default timezone: system */
-	struct timezone tz;
-	if (gettimeofday(NULL, &tz) == 0) {
-		timezone = -tz.tz_minuteswest / 60.0;
-	}
-
 	/* parse mode */
 	if (argc > 1 && argv[1][0] != '-') {
 		if (strcmp(argv[1], "rise") == 0) mode = RISE;
@@ -179,6 +176,9 @@ int main(int argc, char *argv[]) {
 					fprintf(stderr, "invalid date: %s\n", optarg);
 					error = true;
 				}
+				else {
+					mktime(&date); /* update date.tm_gmtoff */
+				}
 				break;
 
 			case 'f':
@@ -217,6 +217,10 @@ int main(int argc, char *argv[]) {
 		}
 	}
 
+	if (timezone == INT_MAX) {
+		timezone = date.tm_gmtoff / 3600;
+	}
+
 	/* validate mode */
 	if (mode == INVALID) {
 		fprintf(stderr, "invalid mode\n");
@@ -268,6 +272,7 @@ int main(int argc, char *argv[]) {
 	printf("calculate for: %s\n", date_str);
 	printf("for position: %f, %f\n", pos.lat, pos.lon);
 	printf("with twilight: %f\n", twilight);
+	printf("with timezone: %d\n", timezone);
 #endif
 
 	/* start the calculation */