Datetime CAML query not working

<Where>

  <Leq>
   <FieldRef Name ='" + internalEndDate + "'/>
   <Value Type ='DateTime'>" + System.DateTime.Now.AddDays(7) + "</Value>
  </Leq>


 </Where>

Current Date
<Where>

  <Leq>
   <FieldRef Name ='" + internalEndDate + "'/>
   <Value Type ='DateTime'>" + System.DateTime.Now+ "</Value>
  </Leq>


 </Where>