--- glib/gtimezone.c.orig	2018-09-21 12:29:23.000000000 +0300

+++ glib/gtimezone.c	2019-09-12 00:53:42.760936000 +0300

@@ -37,6 +37,7 @@

 #include "gslice.h"

 #include "gdatetime.h"

 #include "gdate.h"

+#include "genviron.h"

 #ifdef G_OS_WIN32

 #define STRICT

@@ -187,6 +188,8 @@ struct _GTimeZone

 G_LOCK_DEFINE_STATIC (time_zones);

 static GHashTable/*<string?, GTimeZone>*/ *time_zones;

+G_LOCK_DEFINE_STATIC (tz_local);

+static GTimeZone *tz_local = NULL;

 #define MIN_TZYEAR 1916 /* Daylight Savings started in WWI */

 #define MAX_TZYEAR 2999 /* And it's not likely ever to go away, but

@@ -1457,10 +1460,20 @@ g_time_zone_new (const gchar *identifier)

  *

  * Since: 2.26

  **/

+static gpointer

+g_time_zone_utc_init (gpointer data)

+{

+  return g_time_zone_new ("UTC");

+}

+

 GTimeZone *

 g_time_zone_new_utc (void)

 {

-  return g_time_zone_new ("UTC");

+  static GOnce utc_once = G_ONCE_INIT;

+

+  g_once (&utc_once, g_time_zone_utc_init, NULL);

+

+  return g_time_zone_ref ((GTimeZone *)utc_once.retval);

 }

 /**

@@ -1483,7 +1496,23 @@ g_time_zone_new_utc (void)

 GTimeZone *

 g_time_zone_new_local (void)

 {

-  return g_time_zone_new (getenv ("TZ"));

+  const gchar *tzenv = g_getenv ("TZ");

+  GTimeZone *tz;

+

+  G_LOCK (tz_local);

+

+  /* Is time zone changed and must be flushed? */

+  if (tz_local && g_strcmp0 (tz_local->name, tzenv))

+    g_clear_pointer (&tz_local, g_time_zone_unref);

+

+  if (tz_local == NULL)

+    tz_local = g_time_zone_new (tzenv);

+

+  tz = g_time_zone_ref (tz_local);

+

+  G_UNLOCK (tz_local);

+

+  return tz;

 }

 #define TRANSITION(n)         g_array_index (tz->transitions, Transition, n)