--- /usr/src/lib/libc/stdtime/localtime.c	Mon Jun 14 12:31:52 2004
+++ /usr/src/lib/libc/stdtime/localtime.c	Tue Mar  8 20:51:39 2005
@@ -195,6 +195,7 @@
 
 static char		lcl_TZname[TZ_STRLEN_MAX + 1];
 static int		lcl_is_set;
+int			lcl_tz_is_set_by_Zlo;
 static int		gmt_is_set;
 static pthread_mutex_t	lcl_mutex = PTHREAD_MUTEX_INITIALIZER;
 static pthread_mutex_t	gmt_mutex = PTHREAD_MUTEX_INITIALIZER;
@@ -988,6 +989,11 @@
 		return;
 	}
 
+	/*  N.B. when TZ has changed in the environment, you'll have to call
+	 *  tzset() from your program yourself. Zlo.
+	 */
+	lcl_tz_is_set_by_Zlo = 1;
+
 	if (lcl_is_set > 0 && strcmp(lcl_TZname, name) == 0)
 		return;
 	lcl_is_set = strlen(name) < sizeof lcl_TZname;
@@ -1109,12 +1115,14 @@
 			_pthread_setspecific(localtime_key, p_tm);
 		}
 		_pthread_mutex_lock(&lcl_mutex);
-		tzset_basic();
+		if (!lcl_tz_is_set_by_Zlo)
+			tzset_basic();
 		localsub(timep, 0L, p_tm);
 		_pthread_mutex_unlock(&lcl_mutex);
 		return(p_tm);
 	} else {
-		tzset_basic();
+		if (!lcl_tz_is_set_by_Zlo)
+			tzset_basic();
 		localsub(timep, 0L, &tm);
 		return(&tm);
 	}
@@ -1678,7 +1686,8 @@
 {
 	time_t mktime_return_value;
 	_MUTEX_LOCK(&lcl_mutex);
-	tzset_basic();
+	if (!lcl_tz_is_set_by_Zlo)
+		tzset_basic();
 	mktime_return_value = time1(tmp, localsub, 0L);
 	_MUTEX_UNLOCK(&lcl_mutex);
 	return(mktime_return_value);
@@ -1769,7 +1778,8 @@
 time2posix(t)
 time_t	t;
 {
-	tzset();
+	if (!lcl_tz_is_set_by_Zlo)
+		tzset();
 	return t - leapcorr(&t);
 }
 
@@ -1780,7 +1790,8 @@
 	time_t	x;
 	time_t	y;
 
-	tzset();
+	if (!lcl_tz_is_set_by_Zlo)
+		tzset();
 	/*
 	** For a positive leap second hit, the result
 	** is not unique.  For a negative leap second
--- /usr/src/lib/libc/stdtime/strftime.c	Tue Mar  8 20:23:55 2005
+++ /usr/src/lib/libc/stdtime/strftime.c	Tue Mar  8 20:52:48 2005
@@ -90,7 +90,9 @@
 	char *	p;
 	int	warn;
 
-	tzset();
+	if (!lcl_tz_is_set_by_Zlo)
+		tzset();
+
 	warn = IN_NONE;
 	p = _fmt(((format == NULL) ? "%c" : format), t, s, s + maxsize, &warn);
 #ifndef NO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU
--- /usr/src/lib/libc/stdtime/tzfile.h	Sat Mar 23 00:42:05 2002
+++ /usr/src/lib/libc/stdtime/tzfile.h	Tue Mar  8 20:30:52 2005
@@ -17,6 +17,8 @@
 ** Thank you!
 */
 
+extern int	lcl_tz_is_set_by_Zlo;
+
 /*
 ** ID
 */