diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/GanttPanel.java b/ganttzk/src/main/java/org/zkoss/ganttz/GanttPanel.java
index ed0b1f4cb..a3cf5d647 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/GanttPanel.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/GanttPanel.java
@@ -89,4 +89,16 @@ public class GanttPanel extends XulElement implements AfterCompose {
     public void comingFromAnotherTab() {
         timeTrackerComponent.recreate();
     }
+
+    public void zoomIncrease() {
+        getTimeTracker().zoomIncrease();
+    }
+
+    public void zoomDecrease() {
+        getTimeTracker().zoomDecrease();
+    }
+
+    private TimeTracker getTimeTracker() {
+        return timeTrackerComponent.getTimeTracker();
+    }
 }
\ No newline at end of file
diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/Planner.java b/ganttzk/src/main/java/org/zkoss/ganttz/Planner.java
index 0e60bf8d1..23cc9daeb 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/Planner.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/Planner.java
@@ -111,6 +111,20 @@ public class Planner extends HtmlMacroComponent  {
         }
     }
 
+    public void zoomIncrease() {
+        if (ganttPanel == null) {
+            return;
+        }
+        ganttPanel.zoomIncrease();
+    }
+
+    public void zoomDecrease() {
+        if (ganttPanel == null) {
+            return;
+        }
+        ganttPanel.zoomDecrease();
+    }
+
     public <T> void setConfiguration(PlannerConfiguration<T> configuration) {
         if (configuration == null)
             return;
diff --git a/ganttzk/src/main/resources/web/ganttz/zul/plannerLayout.zul b/ganttzk/src/main/resources/web/ganttz/zul/plannerLayout.zul
index f273e9f48..d962ba930 100644
--- a/ganttzk/src/main/resources/web/ganttz/zul/plannerLayout.zul
+++ b/ganttzk/src/main/resources/web/ganttz/zul/plannerLayout.zul
@@ -1,4 +1,8 @@
 <zk xmlns:n="http://www.zkoss.org/2005/zk/native">
+<zscript><![CDATA[
+planner = self;
+]]>
+</zscript>
     <borderlayout sclass="plannerlayout" width="auto">
        <north height="30px" border="0">
        <hbox align="center">
@@ -6,8 +10,8 @@
         <button label="Back" />
         <button label="Company view" />
         <separator/>
-        <button label="+" />
-        <button label="-" />
+        <button label="+" onClick="planner.zoomIncrease();"/>
+        <button label="-" onClick="planner.zoomDecrease();"/>
         From: <datebox /> to: <datebox />
         <separator/>
         Filter: