diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/data/Milestone.java b/ganttzk/src/main/java/org/zkoss/ganttz/data/Milestone.java
index 3dbf8a52d..d8072347d 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/data/Milestone.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/data/Milestone.java
@@ -28,10 +28,6 @@ import java.util.List;
  */
 public class Milestone extends Task {
 
-    public Milestone() {
-        super();
-    }
-
     public Milestone(ITaskFundamentalProperties fundamentalProperties) {
         super(fundamentalProperties);
     }
diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/data/Task.java b/ganttzk/src/main/java/org/zkoss/ganttz/data/Task.java
index 6e92992f4..0c8da5f15 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/data/Task.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/data/Task.java
@@ -97,34 +97,12 @@ public abstract class Task implements ITaskFundamentalProperties {
         this.fundamentalProperties = fundamentalProperties;
     }
 
-    public Task() {
-        this(new DefaultFundamentalProperties());
-    }
-
     @Override
     public List<Constraint<Date>> getStartConstraints() {
         return violationNotificator.withListener(fundamentalProperties
                 .getStartConstraints());
     }
 
-    public Task(String name, Date beginDate, long lengthMilliseconds) {
-        this();
-        if (name == null) {
-            throw new IllegalArgumentException("name cannot be null");
-        }
-        if (beginDate == null) {
-            throw new IllegalArgumentException("beginDate cannot be null");
-        }
-        if (lengthMilliseconds < 0) {
-            throw new IllegalArgumentException(
-                    "length in milliseconds must be positive. Instead it is "
-                            + lengthMilliseconds);
-        }
-        this.fundamentalProperties.setName(name);
-        this.fundamentalProperties.setBeginDate(beginDate);
-        this.fundamentalProperties.setLengthMilliseconds(lengthMilliseconds);
-    }
-
     public abstract boolean isLeaf();
 
     public abstract boolean isContainer();