diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/TimeTracker.java b/ganttzk/src/main/java/org/zkoss/ganttz/TimeTracker.java
index 1496f1ff9..76ce7f324 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/TimeTracker.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/TimeTracker.java
@@ -110,12 +110,12 @@ public class TimeTracker extends HtmlMacroComponent {
 
     public void onIncrease(int offset) {
         changeDetailLevel(getDetailLevel().next(), offset
-                * getDetailLevel().getTimeTrackerState().pixelsPerDay());
+                * getDetailLevel().getTimeTrackerState().daysPerPixel());
     }
 
     public void onDecrease(int offset) {
         changeDetailLevel(getDetailLevel().previous(), offset
-                * getDetailLevel().getTimeTrackerState().pixelsPerDay());
+                * getDetailLevel().getTimeTrackerState().daysPerPixel());
     }
 
     private void changeDetailLevel(ZoomLevel d, double days) {
@@ -127,7 +127,7 @@ public class TimeTracker extends HtmlMacroComponent {
         fireZoomChanged(d);
 
         scrollHorizontalPercentage((int) Math.floor(days
-                / d.getTimeTrackerState().pixelsPerDay()));
+                / d.getTimeTrackerState().daysPerPixel()));
     }
 
     private ZoomLevel getDetailLevel() {
diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailFiveTimeTrackerState.java b/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailFiveTimeTrackerState.java
index dd3e23341..7d39a5956 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailFiveTimeTrackerState.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailFiveTimeTrackerState.java
@@ -23,7 +23,7 @@ public class DetailFiveTimeTrackerState extends TimeTrackerStateUsingJodaTime {
 
     public static final DetailFiveTimeTrackerState INSTANCE = new DetailFiveTimeTrackerState();
 
-    public final double pixelsPerDay() {
+    public final double daysPerPixel() {
         return ((double) 1 / SECOND_LEVEL_SIZE);
     }
 
diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailFourTimeTrackerState.java b/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailFourTimeTrackerState.java
index c7790bf29..51a77cad4 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailFourTimeTrackerState.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailFourTimeTrackerState.java
@@ -18,7 +18,7 @@ public class DetailFourTimeTrackerState extends TimeTrackerStateUsingJodaTime {
     private static final int FIRST_LEVEL_SIZE = 200;
     private static final int SECOND_LEVEL_SIZE = 50;
 
-    public final double pixelsPerDay() {
+    public final double daysPerPixel() {
         return ((double) 7 / SECOND_LEVEL_SIZE);
     }
 
diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailOneTimeTrackerState.java b/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailOneTimeTrackerState.java
index 2aebb3190..454ae82c6 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailOneTimeTrackerState.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailOneTimeTrackerState.java
@@ -17,7 +17,7 @@ public class DetailOneTimeTrackerState extends TimeTrackerState {
     private static final int FIRST_LEVEL_ITEM_SIZE = 200;
     private static final int SECOND_LEVEL_ITEM_SIZE = 100;
 
-    public final double pixelsPerDay() {
+    public final double daysPerPixel() {
         return ((double) 365 / FIRST_LEVEL_ITEM_SIZE);
     }
 
diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailThreeTimeTrackerState.java b/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailThreeTimeTrackerState.java
index 397883aa3..0af92d09d 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailThreeTimeTrackerState.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailThreeTimeTrackerState.java
@@ -18,7 +18,7 @@ public class DetailThreeTimeTrackerState extends TimeTrackerStateUsingJodaTime {
     private static final int FIRST_LEVEL_SIZE = 300;
     protected static final int SECOND_LEVEL_SIZE = 50;
 
-    public final double pixelsPerDay() {
+    public final double daysPerPixel() {
         return ((double) 182.5 / FIRST_LEVEL_SIZE);
     }
 
diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailTwoTimeTrackerState.java b/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailTwoTimeTrackerState.java
index 47c4965c6..084234a72 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailTwoTimeTrackerState.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/DetailTwoTimeTrackerState.java
@@ -20,7 +20,7 @@ public class DetailTwoTimeTrackerState extends TimeTrackerState {
     private static final int FIRST_LEVEL_ITEM_SIZE = 400;
     private static final int SECOND_LEVEL_ITEM_SIZE = 100;
 
-    public final double pixelsPerDay() {
+    public final double daysPerPixel() {
         return ((double) 365 / FIRST_LEVEL_ITEM_SIZE);
     }
 
diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/TimeTrackerState.java b/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/TimeTrackerState.java
index 866d4b17f..88dc494b5 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/TimeTrackerState.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/util/zoom/TimeTrackerState.java
@@ -203,6 +203,6 @@ public abstract class TimeTrackerState {
 
     public abstract Interval getRealIntervalFor(Interval testInterval);
 
-    public abstract double pixelsPerDay();
+    public abstract double daysPerPixel();
 
 }