Hi,
Yes, it should be possible.
One of our requirement, we were used execution variable inside the timeEventDefinition. we want to repeat the same process after certain interview, so we have used "R1/PT2M" via execution variable.
Here is code snippet.
<code>
<boundaryEvent id="boundarytimer4" name="Timer" attachedToRef="sid-A9FA5F1E-66A8-4E7B-A6AF-A8105A56BDD4" cancelActivity="false">
<timerEventDefinition>
<timeCycle>${dueDateRemainderInterval}</timeCycle>
</timerEventDefinition>
</boundaryEvent>
<serviceTask id="alfrescoScripttask1" name="Calculate timer cycle " activiti:class="org.alfresco.repo.workflow.activiti.script.AlfrescoScriptDelegate">
<extensionElements>
<activiti:field name="script">
<activiti:string><![CDATA[//
dueDateRemainderInterval = "R1/PT2M"
execution.setVariable('dueDateRemainderInterval',dueDateRemainderInterval);
]]></activiti:string>
</activiti:field>
</extensionElements>
</serviceTask>
</code>
In your case, you can try like the below one.
<code>
<timerEventDefinition>
<timeDate>${dateVariable}</timeDate>
</timerEventDefinition>
</code>
Hope this helps you.