Index: contrib/tzcode/stdtime/localtime.c
===================================================================
--- contrib/tzcode/stdtime/localtime.c
+++ contrib/tzcode/stdtime/localtime.c
@@ -170,6 +170,7 @@
 ** Prototypes for static functions.
 */
 
+static int		check_tz_change(int is_lcl_set);
 static long		detzcode(const char * codep);
 static time_t		detzcode64(const char * codep);
 static int		differ_by_repeat(time_t t1, time_t t0);
@@ -235,8 +236,16 @@
 #define TZ_STRLEN_MAX 255
 #endif /* !defined TZ_STRLEN_MAX */
 
+#define TZ_FILENAME     "/etc/localtime"
+#define MAX_CHECK_COUNT 10
+#define CHECK_INTERVAL  10
 static char		lcl_TZname[TZ_STRLEN_MAX + 1];
 static int		lcl_is_set;
+static int		done_env_read = 0;
+static int		watch_changes = 1;            /* Always starts off taking notice */
+static time_t		tzfile_ctime = (time_t)0;     /* will always want the first check */
+static time_t		last_check_time = (time_t)0;  /* It's time to check immediately */
+static int		check_times;
 static pthread_once_t	gmt_once = PTHREAD_ONCE_INIT;
 static pthread_rwlock_t	lcl_rwlock = PTHREAD_RWLOCK_INITIALIZER;
 static pthread_once_t	gmtime_once = PTHREAD_ONCE_INIT;
@@ -270,6 +279,63 @@
 time_t			altzone = 0;
 #endif /* defined ALTZONE */
 
+static int
+check_tz_change(int is_lcl_set)
+{
+	int is_change = 0;
+	if ( watch_changes ) {
+		struct stat buf;
+		time_t  current_time = time(NULL);
+
+		if ( ! done_env_read ) {
+			char *env_ptr;
+
+			env_ptr = getenv("ZONEINFO_WATCH_CHANGES");
+			done_env_read = 1;
+			if (env_ptr == NULL) {
+				watch_changes = 1; /* default value */
+			} else {
+				if (strncmp("yes", env_ptr, 3)) {
+					watch_changes = 0;
+				} else {
+					watch_changes = 1;
+				}
+			}
+		}
+
+		if (check_times++ % MAX_CHECK_COUNT == 0 ||
+			(current_time - last_check_time > CHECK_INTERVAL)) {
+			if (fstatat(AT_FDCWD, TZ_FILENAME, &buf, AT_SYMLINK_NOFOLLOW ) == 0) {
+				if (tzfile_ctime != buf.st_ctime) {
+					tzfile_ctime = buf.st_ctime;
+					is_change = 1;
+				}
+			} else {
+				if (tzfile_ctime != 0) {
+					/* it went away.. do whatever we do with no TZ */
+					is_change = 1;
+					tzfile_ctime = (time_t)0;
+				}
+			}
+			check_times = 0;
+			last_check_time = current_time;
+		}
+	}
+
+	if (is_lcl_set == 0 && is_change == 0) {
+		if ( lcl_is_set >= 0 ) {
+			is_change = 1;
+		}
+	} else if (is_lcl_set == 1 && is_change == 0) {
+		if ( lcl_is_set <= 0) {
+			is_change = 1;
+		}
+	}
+
+	return is_change;
+}
+
+
 static long
 detzcode(const char *const codep)
 {
@@ -1226,7 +1292,7 @@
 {
 	if (!rdlocked)
 		_RWLOCK_RDLOCK(&lcl_rwlock);
-	if (lcl_is_set < 0) {
+	if ((check_tz_change(0) == 0)) {
 		if (!rdlocked)
 			_RWLOCK_UNLOCK(&lcl_rwlock);
 		return;
@@ -1276,7 +1342,7 @@
 
 	if (!rdlocked)
 		_RWLOCK_RDLOCK(&lcl_rwlock);
-	if (lcl_is_set > 0 && strcmp(lcl_TZname, name) == 0) {
+	if (strcmp(lcl_TZname, name) == 0 && check_tz_change(1) == 0 ) {
 		if (!rdlocked)
 			_RWLOCK_UNLOCK(&lcl_rwlock);
 		return;