1 files changed, 38 insertions, 0 deletions
diff --git a/src/lib/utc-offset.c b/src/lib/utc-offset.c
new file mode 100644
index 0000000..d3b4bd2
--- /dev/null
+++ b/src/lib/utc-offset.c
@@ -0,0 +1,38 @@
+/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "utc-offset.h"
+
+#include <sys/time.h>
+
+int utc_offset(struct tm *tm, time_t t ATTR_UNUSED)
+{
+#ifdef HAVE_TM_GMTOFF
+	return (int) (tm->tm_gmtoff/60);
+#else
+	struct tm ltm, gtm;
+	int offset;
+
+	/* gmtime() overwrites tm, so we need to copy it elsewhere */
+	ltm = *tm;
+	tm = gmtime(&t);
+	gtm = *tm;
+
+	/* max offset of 24 hours */
+	if ((ltm.tm_yday < gtm.tm_yday && ltm.tm_year == gtm.tm_year) ||
+	    ltm.tm_year < gtm.tm_year)
+		offset = -24 * 60;
+	else if ((ltm.tm_yday > gtm.tm_yday && ltm.tm_year == gtm.tm_year) ||
+		 ltm.tm_year > gtm.tm_year)
+		offset = 24 * 60;
+	else
+		offset = 0;
+
+	offset += (ltm.tm_hour - gtm.tm_hour) * 60;
+	offset += (ltm.tm_min - gtm.tm_min);
+
+	/* restore overwritten tm */
+	*tm = ltm;
+	return offset;
+#endif
+}