diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/AvailabilityTimeLine.java b/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/AvailabilityTimeLine.java
index 4d2f0559f..d7fc5fcae 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/AvailabilityTimeLine.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/AvailabilityTimeLine.java
@@ -27,6 +27,7 @@ import java.util.List;
 import java.util.ListIterator;
 
 import org.apache.commons.lang.Validate;
+import org.apache.commons.lang.builder.HashCodeBuilder;
 import org.joda.time.LocalDate;
 
 /**
@@ -303,6 +304,21 @@ public class AvailabilityTimeLine {
                     - this.end.compareTo(other.end);
         }
 
+        @Override
+        public boolean equals(Object obj) {
+            if (obj instanceof Interval) {
+                Interval other = (Interval) obj;
+                return start.equals(other.getStart())
+                        && end.equals(other.getEnd());
+            }
+            return false;
+        }
+
+        @Override
+        public int hashCode() {
+            return new HashCodeBuilder().append(start).append(end).toHashCode();
+        }
+
         public boolean includes(LocalDate date) {
             return includes(new FixedPoint(date));
         }
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/common/ProportionalDistributor.java b/navalplanner-business/src/main/java/org/navalplanner/business/common/ProportionalDistributor.java
index ec727edf4..ebe040a39 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/common/ProportionalDistributor.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/common/ProportionalDistributor.java
@@ -53,6 +53,10 @@ public class ProportionalDistributor {
         return result;
     }
 
+    /**
+     * Note: this class has a natural ordering that is inconsistent with equals.
+     *
+     */
     private static class FractionWithPosition implements
             Comparable<FractionWithPosition> {
 
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/labels/entities/LabelType.java b/navalplanner-business/src/main/java/org/navalplanner/business/labels/entities/LabelType.java
index b50d8fac1..2c16c1838 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/labels/entities/LabelType.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/labels/entities/LabelType.java
@@ -38,6 +38,9 @@ import org.navalplanner.business.labels.daos.ILabelTypeDAO;
 
 /**
  * LabeType entity
+ *
+ * Note: this class has a natural ordering that is inconsistent with equals.
+ *
  * @author Diego Pino Garcia<dpino@igalia.com>
  */
 public class LabelType extends IntegrationEntity implements Comparable {
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/Material.java b/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/Material.java
index 4ba49befe..0d5768f54 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/Material.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/Material.java
@@ -29,8 +29,12 @@ import org.navalplanner.business.common.IntegrationEntity;
 import org.navalplanner.business.common.Registry;
 import org.navalplanner.business.materials.bootstrap.UnitTypeBootstrap;
 import org.navalplanner.business.materials.daos.IMaterialDAO;
+
 /**
  * Material entity
+ *
+ * Note: this class has a natural ordering that is inconsistent with equals.
+ *
  * @author Jacobo Aragunde Perez <jaragunde@igalia.com>
  *
  */
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/MaterialAssignment.java b/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/MaterialAssignment.java
index 970bdf01f..e5fa42aea 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/MaterialAssignment.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/MaterialAssignment.java
@@ -30,8 +30,9 @@ import org.navalplanner.business.orders.entities.OrderElement;
 
 /**
  *
- * @author Diego Pino Garcia <dpino@igalia.com>
+ * Note: this class has a natural ordering that is inconsistent with equals.
  *
+ * @author Diego Pino Garcia <dpino@igalia.com>
  */
 public class MaterialAssignment extends BaseEntity implements Comparable {
 
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/MaterialAssignmentTemplate.java b/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/MaterialAssignmentTemplate.java
index 16ea180b0..8ac5807ed 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/MaterialAssignmentTemplate.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/MaterialAssignmentTemplate.java
@@ -27,8 +27,9 @@ import org.navalplanner.business.orders.entities.OrderElement;
 import org.navalplanner.business.templates.entities.OrderElementTemplate;
 
 /**
- * @author Óscar González Fernández <ogonzalez@igalia.com>
+ * Note: this class has a natural ordering that is inconsistent with equals.
  *
+ * @author Óscar González Fernández <ogonzalez@igalia.com>
  */
 public class MaterialAssignmentTemplate extends BaseEntity implements
         Comparable<MaterialAssignmentTemplate> {
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/EffortDistributor.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/EffortDistributor.java
index 19eb783d5..7eb79fdc1 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/EffortDistributor.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/EffortDistributor.java
@@ -240,6 +240,9 @@ public class EffortDistributor {
 
     }
 
+    /**
+     * Note: this class has a natural ordering that is inconsistent with equals.
+     */
     private static class ResourceWithAvailableCapacity implements
             Comparable<ResourceWithAvailableCapacity> {
 
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/limiting/entities/DateAndHour.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/limiting/entities/DateAndHour.java
index d65371875..b9fbf2e34 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/limiting/entities/DateAndHour.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/limiting/entities/DateAndHour.java
@@ -27,6 +27,8 @@ import java.util.Iterator;
 
 import org.apache.commons.lang.ArrayUtils;
 import org.apache.commons.lang.Validate;
+import org.apache.commons.lang.builder.EqualsBuilder;
+import org.apache.commons.lang.builder.HashCodeBuilder;
 import org.joda.time.DateTime;
 import org.joda.time.LocalDate;
 import org.navalplanner.business.workingday.EffortDuration;
@@ -89,6 +91,21 @@ public class DateAndHour implements Comparable<DateAndHour> {
                 .getHour());
     }
 
+    @Override
+    public boolean equals(Object obj) {
+        if (obj instanceof DateAndHour) {
+            DateAndHour other = (DateAndHour) obj;
+            return new EqualsBuilder().append(date, other.date)
+                    .append(hour, other.hour).isEquals();
+        }
+        return false;
+    }
+
+    @Override
+    public int hashCode() {
+        return new HashCodeBuilder().append(date).append(hour).toHashCode();
+    }
+
     private LocalDate getDate(DateAndHour dateAndHour) {
         return (dateAndHour != null) ? dateAndHour.getDate() : null;
     }
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/limiting/entities/Gap.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/limiting/entities/Gap.java
index d46989143..b9e3f6a8a 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/limiting/entities/Gap.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/limiting/entities/Gap.java
@@ -50,6 +50,7 @@ import org.navalplanner.business.workingday.IntraDayDate;
 import org.navalplanner.business.workingday.IntraDayDate.PartialDay;
 
 /**
+ * Note: this class has a natural ordering that is inconsistent with equals.
  *
  * @author Diego Pino Garcia <dpino@igalia.com>
  *
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/reports/dtos/OrderCostsPerResourceDTO.java b/navalplanner-business/src/main/java/org/navalplanner/business/reports/dtos/OrderCostsPerResourceDTO.java
index 46d4d3b0d..dda605cdd 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/reports/dtos/OrderCostsPerResourceDTO.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/reports/dtos/OrderCostsPerResourceDTO.java
@@ -32,6 +32,10 @@ import org.navalplanner.business.resources.entities.Worker;
 import org.navalplanner.business.workreports.entities.WorkReportLine;
 import org.navalplanner.business.workreports.valueobjects.DescriptionValue;
 
+
+/**
+ * Note: this class has a natural ordering that is inconsistent with equals.
+ */
 public class OrderCostsPerResourceDTO implements
         Comparable<OrderCostsPerResourceDTO> {
 
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java b/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java
index 5876103a4..cb1965f32 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java
@@ -30,6 +30,9 @@ import org.navalplanner.business.common.exceptions.InstanceNotFoundException;
 
 /**
  * This class models a worker.
+ *
+ * Note: this class has a natural ordering that is inconsistent with equals.
+ *
  * @author Fernando Bellas Permuy <fbellas@udc.es>
  * @author Susana Montes Pedreira <smontes@wirelessgalicia.com>
  */
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/workreports/entities/WorkReportLabelTypeAssigment.java b/navalplanner-business/src/main/java/org/navalplanner/business/workreports/entities/WorkReportLabelTypeAssigment.java
index 49e3aa325..6126fee55 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/workreports/entities/WorkReportLabelTypeAssigment.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/workreports/entities/WorkReportLabelTypeAssigment.java
@@ -27,6 +27,8 @@ import org.navalplanner.business.labels.entities.Label;
 import org.navalplanner.business.labels.entities.LabelType;
 
 /**
+ * Note: this class has a natural ordering that is inconsistent with equals.
+ *
  * @author Susana Montes Pedreira <smontes@wirelessgalicia.com>
  */
 public class WorkReportLabelTypeAssigment extends BaseEntity implements
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/workreports/entities/WorkReportLine.java b/navalplanner-business/src/main/java/org/navalplanner/business/workreports/entities/WorkReportLine.java
index c02ffbbb5..dc6b9d265 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/workreports/entities/WorkReportLine.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/workreports/entities/WorkReportLine.java
@@ -45,6 +45,8 @@ import org.navalplanner.business.workreports.valueobjects.DescriptionField;
 import org.navalplanner.business.workreports.valueobjects.DescriptionValue;
 
 /**
+ * Note: this class has a natural ordering that is inconsistent with equals.
+ *
  * @author Diego Pino García <dpino@igalia.com>
  * @author Susana Montes Pedreira <smontes@wirelessgalicia.com>
  */
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/limitingresources/GapsMergeSort.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/limitingresources/GapsMergeSort.java
index 1946a0176..4126f1f4f 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/limitingresources/GapsMergeSort.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/limitingresources/GapsMergeSort.java
@@ -39,6 +39,10 @@ public class GapsMergeSort {
     private GapsMergeSort() {
     }
 
+    /**
+     * Note: this class has a natural ordering that is inconsistent with equals.
+     *
+     */
     private static class CurrentGap implements Comparable<CurrentGap> {
 
         static List<CurrentGap> convert(
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/limitingresources/LimitingResourcesController.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/limitingresources/LimitingResourcesController.java
index c1ac4c228..7a7314103 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/limitingresources/LimitingResourcesController.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/limitingresources/LimitingResourcesController.java
@@ -257,6 +257,8 @@ public class LimitingResourcesController extends GenericForwardComposer {
     /**
      * DTO for list of unassigned {@link LimitingResourceQueueElement}
      *
+     * Note: this class has a natural ordering that is inconsistent with equals.
+     *
      * @author Diego Pino Garcia <dpino@igalia.com>
      *
      */
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/HoursGroupWrapper.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/HoursGroupWrapper.java
index be727de9b..20e857a23 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/HoursGroupWrapper.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/HoursGroupWrapper.java
@@ -43,6 +43,9 @@ import org.navalplanner.business.templates.entities.OrderLineGroupTemplate;
 /**
  * Wrapper represents the handled data in the form of assigning criterion
  * requirement.
+ *
+ * Note: this class has a natural ordering that is inconsistent with equals.
+ *
  * @author Susana Montes Pedreira <smontes@wirelessgalicia.com>
  */
 public class HoursGroupWrapper implements INewObject,