Codeigniter - Date format - Form Validation

I have a pretty clean solution for this. You can extend codeigniters form validation library.

Do this by putting a MY_Form_validation.php file in your application/libraries folder. This file should look like this:

class MY_Form_validation extends CI_Form_validation {

    public function __construct($rules = array()) {
        parent::__construct($rules);
    }


    public function valid_date($date) {
        $d = DateTime::createFromFormat('Y-m-d', $date);
        return $d && $d->format('Y-m-d') === $date;
    }
}

To add the error message, you go to your application/language/ folder and open the form_validation_lang.php file. Add an entry to the $lang array at the end of the file, like so:

$lang['form_validation_valid_date'] = 'The field {field} is not a valid date';

Note that the key here must be the same as the function name (valid_date).

Then in your controller you use this as any other form validation function like for example 'required'

$this->form_validation->set_rules('date','Date','trim|required|valid_date');

I know this is old, but I just encountered the same issue. I like the answer Winks provided, but found that the code did not work. I modified it to this:

  public function your_form_handler($date)
  {
    // ....
    $this->form_validation->set_rules('date', 'Date', 'required|callback_date_valid');
    // ....
  }

  /**
   * Validate dd/mm/yyyy
   */
  public function date_valid($date)
  {
    $parts = explode("/", $date);
    if (count($parts) == 3) {      
      if (checkdate($parts[1], $parts[0], $parts[2]))
      {
        return TRUE;
      }
    }
    $this->form_validation->set_message('date_valid', 'The Date field must be mm/dd/yyyy');
    return false;
  }

you can do it with regex

$this->form_validation->set_rules('reg[dob]', 'Date of birth', 'regex_match[(0[1-9]|1[0-9]|2[0-9]|3(0|1))-(0[1-9]|1[0-2])-\d{4}]'); 

You can take use of CodeIgniters callback functions by creating a callback_date_valid() function that check if the date is valid.

And to check if it is valid, you could use PHP's checkdate function

array(
  'field' => 'reg[dob]',
  'label' => 'DOB',
  'rules' => 'required|date_valid'
)

function callback_date_valid($date){
    $day = (int) substr($date, 0, 2);
    $month = (int) substr($date, 3, 2);
    $year = (int) substr($date, 6, 4);
    return checkdate($month, $day, $year);
}