Querying a date column with Laravel's query builder

When writing a query against a table with a date column using the Laravel query builder, what data type should be used? The following should return 13 results but instead returns nothing:

$date = new \DateTime("-2 days");
Model::whereDate($date)->get();

Dumping the query shows that laravel is trying this:

array(3) {
  'query' =>
  string(62) "select * from `table` where `date` = ?"
  'bindings' =>
  array(1) {
    [0] =>
    class DateTime#310 (3) {
      public $date =>
      string(19) "2013-10-07 14:39:11"
      public $timezone_type =>
      int(3)
      public $timezone =>
      string(3) "UTC"
    }
  }
  'time' =>
  double(5.55)
}

Writing the query as Model::whereDate($date->format("Y-m-d"))->get() instead works but doesn't seem like the Laravel way to do it.

Is there a specific object type I should be passing into the query to filter by a date column?

EDIT: The model in this example looks like this:

class Model extends Eloquent {
    protected $table = 'table';

    public function getDates() {
        return array('date');
    }
}

The table it refers to looks like this:

CREATE TABLE table(
  some_field VARCHAR(255),
  date DATE
) ENGINE = 'InnoDB';

Laravel thinks the date column is a string: Model::lists('date') returns an array of strings, as does DB::table('table')->lists('date').

Changing $date = new \DateTime("-2 days"); to $date = \Carbon\Carbon::now()->subDays(2) doesn't allow me to query the date column directly with the Carbon object.

UPDATED: For whatever reason, the built-in MySQL date to \Carbon\Carbon isn't working for me, so the simplest solution was to write one as a query scope:

public function scopeDate($query, \Carbon\Carbon $date) {
    return $query->whereDate($date->toDateString());
}