[Mick]

This thread is a little old but the method still works on 4.78! The only issue is that the multi-edit is not supported but adding an extra line like so rectifies even this. A must have mod for those users with Hot Products or New Arrivals.

Code change on main/product_details.tpl

<tr>
  {* New Line Here *}
  {if $geid ne ''}<td width="15" class="TableSubHead"><input type="checkbox" value="Y" name="fields[add_date]" /></td>{/if}

  <td class="FormButton" nowrap="nowrap">{$lng.lbl_date_added}:</td>  
  <td class="ProductDetails">
    {include file="main/datepicker.tpl" name="add_date" date=$product.add_date}
  </td>
</tr>

A thank-you for the original post by ADDISON