diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/costcategories/entities/ResourcesCostCategoryAssignment.java b/navalplanner-business/src/main/java/org/navalplanner/business/costcategories/entities/ResourcesCostCategoryAssignment.java
index d970186a9..91bcda50c 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/costcategories/entities/ResourcesCostCategoryAssignment.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/costcategories/entities/ResourcesCostCategoryAssignment.java
@@ -20,6 +20,7 @@
 
 package org.navalplanner.business.costcategories.entities;
 
+import org.hibernate.validator.AssertTrue;
 import org.hibernate.validator.NotNull;
 import org.joda.time.LocalDate;
 import org.navalplanner.business.common.BaseEntity;
@@ -88,4 +89,12 @@ public class ResourcesCostCategoryAssignment extends BaseEntity {
             resource.addResourcesCostCategoryAssignment(this);
         }
     }
+
+    @AssertTrue(message="The end date cannot be before the init date")
+    public boolean checkPositiveTimeInterval() {
+        if (endDate == null) {
+            return true;
+        }
+        return (endDate.isAfter(initDate) || initDate.equals(endDate));
+    }
 }
diff --git a/navalplanner-business/src/test/java/org/navalplanner/business/test/costcategories/daos/ResourcesCostCategoryAssignmentDAOTest.java b/navalplanner-business/src/test/java/org/navalplanner/business/test/costcategories/daos/ResourcesCostCategoryAssignmentDAOTest.java
index d4e48b46b..c8961eb41 100644
--- a/navalplanner-business/src/test/java/org/navalplanner/business/test/costcategories/daos/ResourcesCostCategoryAssignmentDAOTest.java
+++ b/navalplanner-business/src/test/java/org/navalplanner/business/test/costcategories/daos/ResourcesCostCategoryAssignmentDAOTest.java
@@ -34,6 +34,7 @@ import org.joda.time.LocalDate;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.navalplanner.business.common.exceptions.InstanceNotFoundException;
+import org.navalplanner.business.common.exceptions.ValidationException;
 import org.navalplanner.business.costcategories.daos.ICostCategoryDAO;
 import org.navalplanner.business.costcategories.daos.IResourcesCostCategoryAssignmentDAO;
 import org.navalplanner.business.costcategories.entities.CostCategory;
@@ -131,4 +132,13 @@ public class ResourcesCostCategoryAssignmentDAOTest {
         assignment.setResource(null);
         assertFalse(resource.getResourcesCostCategoryAssignments().contains(assignment));
     }
+
+    @Test(expected=ValidationException.class)
+    public void testPositiveTimeInterval() {
+        ResourcesCostCategoryAssignment assignment = createValidResourcesCostCategoryAssignment();
+        assignment.setInitDate(new LocalDate(2000,12,31));
+        assignment.setEndDate(new LocalDate(2000,12,1));
+
+        resourcesCostCategoryAssignmentDAO.save(assignment);
+    }
 }