UIDatePicker with "done" button

With Swift

// Place this code inside your ViewController or where you want ;)

var txtField: UITextField = UITextField(frame: CGRectMake(0, 0, 200, 50))

// the formatter should be "compliant" to the UIDatePickerMode selected below
var dateFormatter: NSDateFormatter {
    let formatter = NSDateFormatter()
    // customize the locale for the formatter if you want
    //formatter.locale = NSLocale(localeIdentifier: "it_IT")
    formatter.dateFormat = "dd/MM/yyyy"
    return formatter
}

override func viewDidLoad() {
    super.viewDidLoad()

    // date picker setup
    let datePickerView:UIDatePicker = UIDatePicker()

    // choose the mode you want
    // other options are: DateAndTime, Time, CountDownTimer
    datePickerView.datePickerMode = UIDatePickerMode.Date

    // choose your locale or leave the default (system)
    //datePickerView.locale = NSLocale.init(localeIdentifier: "it_IT")

    datePickerView.addTarget(self, action: "onDatePickerValueChanged:", forControlEvents: UIControlEvents.ValueChanged)
    txtField.inputView = datePickerView

    // datepicker toolbar setup
    let toolBar = UIToolbar()
    toolBar.barStyle = UIBarStyle.Default
    toolBar.translucent = true
    let space = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.FlexibleSpace, target: nil, action: nil)
    let doneButton = UIBarButtonItem(title: "Done", style: UIBarButtonItemStyle.Done, target: self, action: "doneDatePickerPressed")

    // if you remove the space element, the "done" button will be left aligned
    // you can add more items if you want
    toolBar.setItems([space, doneButton], animated: false)
    toolBar.userInteractionEnabled = true
    toolBar.sizeToFit()

    txtField.inputAccessoryView = toolBar

    self.view.addSubview(txtField)
}

func doneDatePickerPressed(){
    self.view.endEditing(true)
}

func onDatePickerValueChanged(datePicker: UIDatePicker) {
    self.txtField = dateFormatter.stringFromDate(datePicker.date)
}

Create a date picker, then add it as the input view of the field in question (self.fieldInQuestion.inputView = datePicker). Next, create a UIToolBar (height 44) with UIBarButton Item on it with the title "Done", target of self, and a selector (ex. @selector(done)). Add this as the input accessory view of the same field you made the date picker an input view for (self.fieldInQuestion.inputAccessoryView = UIToolbarInstance). In the selector method (-(void)done in the example above), make sure you use [self.fieldInQuestion resignFirstResponder] and it will dismiss it.