diff --git a/modules/activiti-engine/src/main/java/org/activiti/engine/impl/calendar/DueDateBusinessCalendar.java b/modules/activiti-engine/src/main/java/org/activiti/engine/impl/calendar/DueDateBusinessCalendar.java
index c821b149e20ed25fcffd2d7075e67b6a2ce97f67..d6f9bcc10288bf51db59a4cbd0e9dfc4158956c4 100644
--- a/modules/activiti-engine/src/main/java/org/activiti/engine/impl/calendar/DueDateBusinessCalendar.java
+++ b/modules/activiti-engine/src/main/java/org/activiti/engine/impl/calendar/DueDateBusinessCalendar.java
@@ -16,6 +16,7 @@ import java.util.Date;
 
 import org.activiti.engine.ActivitiException;
 import org.joda.time.DateTime;
+import org.joda.time.Period;
 
 
 public class DueDateBusinessCalendar implements BusinessCalendar {
@@ -24,6 +25,12 @@ public class DueDateBusinessCalendar implements BusinessCalendar {
   
   public Date resolveDuedate(String duedate) {
     try {
+    	
+    	// check if due period was specified
+    	if(duedate.startsWith("P")){
+    		return DateTime.now().plus(Period.parse(duedate)).toDate();
+    	}
+    	
       return DateTime.parse(duedate).toDate();
 
     } catch (Exception e) {
diff --git a/modules/activiti-engine/src/test/java/org/activiti/engine/test/bpmn/usertask/TaskDueDateExtensionsTest.java b/modules/activiti-engine/src/test/java/org/activiti/engine/test/bpmn/usertask/TaskDueDateExtensionsTest.java
index 1575c160d84a2ec262f0aca07f793172bc391f5a..88749d6112ed2399b56903757922a4147bc043e3 100644
--- a/modules/activiti-engine/src/test/java/org/activiti/engine/test/bpmn/usertask/TaskDueDateExtensionsTest.java
+++ b/modules/activiti-engine/src/test/java/org/activiti/engine/test/bpmn/usertask/TaskDueDateExtensionsTest.java
@@ -22,6 +22,7 @@ import org.activiti.engine.impl.test.PluggableActivitiTestCase;
 import org.activiti.engine.runtime.ProcessInstance;
 import org.activiti.engine.task.Task;
 import org.activiti.engine.test.Deployment;
+import org.joda.time.Period;
 
 
 /**
@@ -60,4 +61,22 @@ public class TaskDueDateExtensionsTest extends PluggableActivitiTestCase {
     Date date = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss").parse("06-07-1986 12:10:00");
     assertEquals(date, task.getDueDate());
   }
+  
+  @Deployment
+  public void testRelativeDueDateStringExtension() throws Exception {
+    
+    Map<String, Object> variables = new HashMap<String, Object>();
+    variables.put("dateVariable", "P2DT5H40M");
+    
+    // Start process-instance, passing ISO8601 duration formatted String that should be used to calculate dueDate
+    ProcessInstance processInstance = runtimeService.startProcessInstanceByKey("dueDateExtension", variables);
+    
+    Task task = taskService.createTaskQuery().processInstanceId(processInstance.getId()).singleResult();
+    
+    assertNotNull(task.getDueDate());
+    Period period = new Period(task.getCreateTime().getTime(), task.getDueDate().getTime());
+    assertEquals(period.getDays(), 2);
+    assertEquals(period.getHours(), 5);
+    assertEquals(period.getMinutes(), 40);
+  }
 }
diff --git a/modules/activiti-engine/src/test/resources/org/activiti/engine/test/bpmn/usertask/TaskDueDateExtensionsTest.testRelativeDueDateStringExtension.bpmn20.xml b/modules/activiti-engine/src/test/resources/org/activiti/engine/test/bpmn/usertask/TaskDueDateExtensionsTest.testRelativeDueDateStringExtension.bpmn20.xml
new file mode 100644
index 0000000000000000000000000000000000000000..5897810e252c27d14130b7621897e6e534c70411
--- /dev/null
+++ b/modules/activiti-engine/src/test/resources/org/activiti/engine/test/bpmn/usertask/TaskDueDateExtensionsTest.testRelativeDueDateStringExtension.bpmn20.xml
@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<definitions id="taskAssigneeExample" 
+  xmlns="http://www.omg.org/spec/BPMN/20100524/MODEL"
+  xmlns:activiti="http://activiti.org/bpmn"
+  targetNamespace="Examples">
+  
+  <process id="dueDateExtension">
+  
+    <startEvent id="theStart" />
+    
+    <sequenceFlow id="flow1" sourceRef="theStart" targetRef="theTask" />
+
+    <userTask id="theTask" name="my task" activiti:dueDate="${dateVariable}" />
+    
+    <sequenceFlow id="flow2" sourceRef="theTask" targetRef="theEnd" />
+    
+    <endEvent id="theEnd" />
+    
+  </process>
+
+</definitions>
\ No newline at end of file