How can I tell if a browser supports <input type='date'>

> Possible Duplicate:
> HTML5 Type Detection and Plugin Initialization

<input type=date>

Should create an input with an (optional) user-agent provided datepicker, but its not widely supported yet, so we're using a jQuery UI Datepicker. How can we allow browsers to use their own datepicker and fall back on jQuery UI only if the browser doesn't have such a thing?

At present I think only Opera has a built in datepicker, but a test for Opera would obviously be bad. Is there a way this feature can be detected (if it can at all in a portable manner)?

The method bellow checks if some input type is supported by most of the browsers:

function checkInput(type) {
	var input = document.createElement("input");
	input.setAttribute("type", type);
	return input.type == type;
}

But, as simonox mentioned in the comments, some browsers (as Android stock browsers) pretend that they support some type (as date), but they do not offer an UI for date inputs. So simonox improved the implementation using the trick of setting an illegal value into the date field. If the browser sanitises this input, it could also offer a datepicker!!!

function checkDateInput() {
	var input = document.createElement('input');
	input.setAttribute('type','date');
	
	var notADateValue = 'not-a-date';
	input.setAttribute('value', notADateValue); 
	
	return (input.value !== notADateValue);
}