--- old/src/java.base/share/classes/java/time/ZoneId.java	2015-02-22 20:39:44.555107230 +0100
+++ new/src/java.base/share/classes/java/time/ZoneId.java	2015-02-22 20:39:44.456108970 +0100
@@ -61,6 +61,8 @@
  */
 package java.time;
 
+import sun.misc.SharedSecrets;
+
 import java.io.DataOutput;
 import java.io.IOException;
 import java.io.InvalidObjectException;
@@ -271,7 +273,7 @@
      * @throws ZoneRulesException if the converted zone region ID cannot be found
      */
     public static ZoneId systemDefault() {
-        return TimeZone.getDefault().toZoneId();
+        return SharedSecrets.getJavaUtilTimeZoneAccess().getDefaultRef().toZoneId();
     }
 
     /**
--- old/src/java.base/share/classes/java/util/TimeZone.java	2015-02-22 20:39:44.871101675 +0100
+++ new/src/java.base/share/classes/java/util/TimeZone.java	2015-02-22 20:39:44.742103943 +0100
@@ -42,6 +42,9 @@
 import java.security.AccessController;
 import java.security.PrivilegedAction;
 import java.time.ZoneId;
+
+import sun.misc.JavaUtilTimeZoneAccess;
+import sun.misc.SharedSecrets;
 import sun.security.action.GetPropertyAction;
 import sun.util.calendar.ZoneInfo;
 import sun.util.calendar.ZoneInfoFile;
@@ -131,6 +134,16 @@
  * @since        1.1
  */
 abstract public class TimeZone implements Serializable, Cloneable {
+
+    static {
+        SharedSecrets.setJavaUtilTimeZoneAccess(new JavaUtilTimeZoneAccess() {
+            @Override
+            public TimeZone getDefaultRef() {
+                return TimeZone.getDefaultRef();
+            }
+        });
+    }
+
     /**
      * Sole constructor.  (For invocation by subclass constructors, typically
      * implicit.)
@@ -293,6 +306,7 @@
             throw new NullPointerException();
         }
         this.ID = ID;
+        this.zoneId = null; // invalidate cache
     }
 
     /**
@@ -544,16 +558,22 @@
      * @since 1.8
      */
     public ZoneId toZoneId() {
-        String id = getID();
-        if (ZoneInfoFile.useOldMapping() && id.length() == 3) {
-            if ("EST".equals(id))
-                return ZoneId.of("America/New_York");
-            if ("MST".equals(id))
-                return ZoneId.of("America/Denver");
-            if ("HST".equals(id))
-                return ZoneId.of("America/Honolulu");
+        ZoneId zId = zoneId;
+        if (zId == null) {
+            String id = getID();
+            if (ZoneInfoFile.useOldMapping() && id.length() == 3) {
+                if ("EST".equals(id))
+                    zId = ZoneId.of("America/New_York");
+                else if ("MST".equals(id))
+                    zId = ZoneId.of("America/Denver");
+                else if ("HST".equals(id))
+                    zId = ZoneId.of("America/Honolulu");
+            } else {
+                zId = ZoneId.of(id, ZoneId.SHORT_IDS);
+            }
+            zoneId = zId;
         }
-        return ZoneId.of(id, ZoneId.SHORT_IDS);
+        return zId;
     }
 
     private static TimeZone getTimeZone(String ID, boolean fallback) {
@@ -710,7 +730,7 @@
             sm.checkPermission(new PropertyPermission
                                ("user.timezone", "write"));
         }
-        defaultTimeZone = zone;
+        defaultTimeZone = (TimeZone) zone.clone();
     }
 
     /**
@@ -735,9 +755,7 @@
     public Object clone()
     {
         try {
-            TimeZone other = (TimeZone) super.clone();
-            other.ID = ID;
-            return other;
+            return super.clone();
         } catch (CloneNotSupportedException e) {
             throw new InternalError(e);
         }
@@ -759,6 +777,12 @@
      * @serial
      */
     private String           ID;
+
+    /**
+     * Cached {@link ZoneId} for this TimeZone
+     */
+    private transient ZoneId zoneId;
+
     private static volatile TimeZone defaultTimeZone;
 
     static final String         GMT_ID        = "GMT";
--- old/src/java.base/share/classes/sun/misc/SharedSecrets.java	2015-02-22 20:39:45.181096227 +0100
+++ new/src/java.base/share/classes/sun/misc/SharedSecrets.java	2015-02-22 20:39:45.066098248 +0100
@@ -53,6 +53,7 @@
     private static JavaIOFileDescriptorAccess javaIOFileDescriptorAccess;
     private static JavaSecurityProtectionDomainAccess javaSecurityProtectionDomainAccess;
     private static JavaSecurityAccess javaSecurityAccess;
+    private static JavaUtilTimeZoneAccess javaUtilTimeZoneAccess;
     private static JavaUtilZipFileAccess javaUtilZipFileAccess;
     private static JavaAWTAccess javaAWTAccess;
     private static JavaAWTFontAccess javaAWTFontAccess;
@@ -164,6 +165,16 @@
         return javaSecurityAccess;
     }
 
+    public static JavaUtilTimeZoneAccess getJavaUtilTimeZoneAccess() {
+        if (javaUtilTimeZoneAccess == null)
+            unsafe.ensureClassInitialized(java.util.TimeZone.class);
+        return javaUtilTimeZoneAccess;
+    }
+
+    public static void setJavaUtilTimeZoneAccess(JavaUtilTimeZoneAccess access) {
+        javaUtilTimeZoneAccess = access;
+    }
+
     public static JavaUtilZipFileAccess getJavaUtilZipFileAccess() {
         if (javaUtilZipFileAccess == null)
             unsafe.ensureClassInitialized(java.util.zip.ZipFile.class);
--- /dev/null	2015-02-22 16:29:22.615854330 +0100
+++ new/src/java.base/share/classes/sun/misc/JavaUtilTimeZoneAccess.java	2015-02-22 20:39:45.375092817 +0100
@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package sun.misc;
+
+import java.util.TimeZone;
+
+public interface JavaUtilTimeZoneAccess {
+    public TimeZone getDefaultRef();
+}
+