$installer->addAttribute("customer", "creation_date",  array(
  "type"          => "varchar",
  "backend"       => "eav/entity_attribute_backend_array",
  "label"         => "",
  "input"         => "date",
  "source"        => "module/attribute_source_customerproducts",
  "visible"       => false,
  "required"      => false,
  "default"       => "",
  "frontend"      => "",
  "unique"        => false,
  "note"          => ""
));