How do i make a timer that shows up on screen?

OK so I am working on a plat-former and I am having trouble displaying a timer on screen if you could tell me how to make one in c# that would be AMAZING!

using UnityEngine;
using System.Collections;

public class Timer : MonoBehaviour {
   void OnGUI(){
        float theTime = Time.deltaTime;
	GUI.Label (new Rect (0,0,250,250),"Time: " + theTime );

the timer should be on the left top of screen
i think dis works, didnt check