diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java b/ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java
index a2bb53ce2..ba6d9475e 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java
@@ -231,6 +231,7 @@ public class LeftTasksTreeRow extends GenericForwardComposer {
                         new DateTime(new GregorianCalendar(minimumYear, MINIMUM_MONTH, MINIMUM_DAY).getTime());
 
                 SimpleDateFormat simpleDateFormat = new SimpleDateFormat("MM/dd/yy");
+
                 // Need to call dateFormat.set2DigitYearStart to force parser not to parse date to previous century
                 simpleDateFormat.set2DigitYearStart(
                         new GregorianCalendar(CALENDAR_START_YEAR, MINIMUM_MONTH, MINIMUM_DAY).getTime());
@@ -250,6 +251,7 @@ public class LeftTasksTreeRow extends GenericForwardComposer {
                         DateTime correct = new DateTime(value);
                         String year = Integer.valueOf(correct.getYear()).toString().substring(2);
 
+                        // TODO Resolve deprecated methods
                         date = simpleDateFormat
                                 .parse(((Date) value).getMonth() + "/" + ((Date) value).getDate() + "/" + year);
 
@@ -260,7 +262,8 @@ public class LeftTasksTreeRow extends GenericForwardComposer {
                 else {
                     try {
                         date = simpleDateFormat.parse((String) value);
-                    } catch (ParseException ignored) {}
+                    } catch (ParseException ignored) {
+                    }
                 }
 
                 DateTime dateTimeInTextbox = new DateTime(date);
diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/data/GanttDiagramGraph.java b/ganttzk/src/main/java/org/zkoss/ganttz/data/GanttDiagramGraph.java
index b52d58189..67a01919c 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/data/GanttDiagramGraph.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/data/GanttDiagramGraph.java
@@ -418,10 +418,22 @@ public class GanttDiagramGraph<V, D extends IDependency<V>> implements ICritical
         }
     }
 
+    /**
+     * This class is designed for performing topological sorting of nodes.
+     * Topological sorting is used to make graph nodes not to be mixed, because
+     * parent and child nodes ({@link TaskPoint}) must be placed in the correct order.
+     * Also during topological sorting nodes are placed on appropriate levels.
+     * Topological sorting can be done using different algorithms, but here is used Khan's algorithm.
+     */
     class TopologicalSorter {
 
         private Map<TaskPoint, Integer> taskPointsByDepthCached = null;
 
+        /**
+         * This method is used to place each node on appropriate level.
+         *
+         * @return map of TaskPoints with appropriate levels
+         */
         private Map<TaskPoint, Integer> taskPointsByDepth() {
             if ( taskPointsByDepthCached != null ) {
                 return taskPointsByDepthCached;
@@ -430,27 +442,47 @@ public class GanttDiagramGraph<V, D extends IDependency<V>> implements ICritical
             Map<TaskPoint, Integer> result = new HashMap<>();
             Map<TaskPoint, Set<TaskPoint>> visitedBy = new HashMap<>();
 
+            /*
+             * Here are stored taskpoints that we have visited.
+             * This need to be done because we need to check have we visited this taskpoint, or not.
+             * Described above need to be done to avoid loop between taskpoints.
+             */
+            Set<TaskPoint> visitedTaskPoints = new HashSet ();
+
             Queue<TaskPoint> withoutIncoming = getInitial(withoutVisibleIncomingDependencies(getTopLevelTasks()));
             for (TaskPoint each : withoutIncoming) {
                 initializeIfNeededForKey(result, each, 0);
             }
 
             while (!withoutIncoming.isEmpty()) {
+
                 TaskPoint current = withoutIncoming.poll();
 
+                visitedTaskPoints.add(current); // Marking taskpoint as visited
+
+                // Taking all child elements
                 for (TaskPoint each : current.getImmediateSuccessors()) {
 
-                    initializeIfNeededForKey(visitedBy, each, new HashSet<TaskPoint>());
-                    Set<TaskPoint> visitors = visitedBy.get(each);
-                    visitors.add(current);
-                    Set<TaskPoint> predecessorsRequired = each.getImmediatePredecessors();
+                    if (!visitedTaskPoints.contains(each)) {
 
-                    if ( visitors.containsAll(predecessorsRequired) ) {
-                        initializeIfNeededForKey(result, each, result.get(current) + 1);
-                        withoutIncoming.offer(each);
+                        initializeIfNeededForKey(visitedBy, each, new HashSet<TaskPoint>());
+
+                        Set<TaskPoint> visitors = visitedBy.get(each);
+                        visitors.add(current);
+
+                        // Taking parent elements
+                        Set<TaskPoint> predecessorsRequired = each.getImmediatePredecessors();
+
+                        if ( visitors.containsAll(predecessorsRequired) ) {
+
+                            initializeIfNeededForKey(result, each, result.get(current) + 1);
+
+                            withoutIncoming.offer(each);
+                        }
                     }
                 }
             }
+
             return taskPointsByDepthCached = Collections.unmodifiableMap(result);
         }
 
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 8ac256488..302f54146 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/data/Task.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/data/Task.java
@@ -497,10 +497,6 @@ public abstract class Task implements ITaskFundamentalProperties {
         return LocalDate.fromDateFields(getBeginDate().toDayRoundedDate());
     }
 
-    public LocalDate getEndDateAsLocalDate() {
-        return LocalDate.fromDateFields(getEndDate().toDayRoundedDate());
-    }
-
     @Override
     public boolean isManualAnyAllocation() {
         return fundamentalProperties.isManualAnyAllocation();
diff --git a/ganttzk/src/main/resources/i18n/keys.pot b/ganttzk/src/main/resources/i18n/keys.pot
index ba4662eb7..e3031297b 100644
--- a/ganttzk/src/main/resources/i18n/keys.pot
+++ b/ganttzk/src/main/resources/i18n/keys.pot
@@ -246,17 +246,17 @@ msgstr ""
 msgid "Show critical path"
 msgstr ""
 
-#: ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java:240
-#: ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java:247
+#: ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java:271
+#: ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java:278
 msgid "The date you entered is invalid"
 msgstr ""
 
-#: ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java:241
-#: ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java:248
+#: ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java:272
+#: ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java:279
 msgid "Please enter date not before"
 msgstr ""
 
-#: ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java:242
-#: ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java:249
+#: ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java:273
+#: ganttzk/src/main/java/org/zkoss/ganttz/LeftTasksTreeRow.java:280
 msgid "and no later than"
 msgstr ""
\ No newline at end of file