problem with set system time to workflow property

[addonin]

Hello!
Excuse me for possible language mistakes, I am not native speaker.
I make workflow and encountered with problem. I have property in content model:

<aspect name="astItRequest:requestProperties">
      <properties>
                     <property name="astItRequest:date">
                     <title>Some date</title>
                     <type>d:date</type>
                     </property>
………………………‍‍‍‍‍‍‍

And I use same property in workflow model (through aspect):

<type name="astItRequestWorkflowModel:submitRequestTask">
   <parent>bpm:startTask</parent>
   <mandatory-aspects>
      <aspect>astItRequest:requestProperties</aspect>
……………………….‍‍‍‍‍

Then I start workflow, I try to set "astItRequest:date" property with real time:

<start-state name="start">
    <task name="astItRequestWorkflowModel:submitRequestTask" swimlane="initiator" />
    <transition name="" to="request">
   <action class="org.alfresco.repo.workflow.jbpm.AlfrescoJavaScript">
      <runas>admin</runas>
      <script>
         &lt;
                            var date = new Date();
                            executionContext.setVariable("astItRequest_date", date);
                            logger.log(executionContext.getVariable("astItRequest_date")); // just for output in catalina.out
                        &gt;            
      </script>
   </action>
</transition>‍‍‍‍‍‍‍‍‍‍‍‍‍‍

and receive next error (in catalina.out):

2012-08-07 05:30:45,542  DEBUG [repo.jscript.ScriptLogger] [http-8080-46] org.alfresco.service.cmr.workflow.WorkflowException: 07070163 Failed to signal transition null from workflow task jbpm$658

I don`t understand why I can`t do it, any suggestions? Maybe data type in content model and data type in workflow are not same types?
Thanks for help.

[addonin]

P.S. forgot to add: I use Alfresco 4.0.d on Ubuntu server 10.04 and jBPM engine for workflow