[pairodimes]

Ok - I read another thread and found the SQL table that contains the Admin Drop Down information for sorting products.

just add your new 'add_date' to the "xcart_config" table - sort by 'title' field - look for the row "product_order" -> look for the field 'varients' -> edit this content to include our new date field.

ex:
add_date:
adddate: lbl_add_date
productcode:lbl_sku
title:lbl_product
orderby: lbl_default
price:lbl_price

this should now show up in the Admin drop down.