Hallo Zach,
I'm not sure, but I think you have to set the eval of the corresponding field
to date or datetime in the TCA array.
example
"mydate" => Array (
      "exclude" => 0,
	  "label" => "Date"
	  "config" => Array (
		"type" => "input",
		"size" => "10",
		"max" => "10",
		"eval" => "date"
	  )
   )
Ursula