Restart timer?

Noob question here. How can I reset the timer or initialize it back starting to zero after changing scenes, etc?

    public Text counterText;

    public float seconds, minutes;

    // Initialization
    void Start()
    {
        counterText = GetComponent<Text>() as Text;
    }

    // Update once per frame
    void Update()
    {
        minutes = (int)(Time.time/60f);
        seconds = (int)(Time.time % 60f);
        counterText.text = minutes.ToString("00") + ":" + seconds.ToString("00");
    }

public Text counterText;

 public float seconds, minutes, startTime;

 // Initialization
 void Start()
 {
     counterText = GetComponent<Text>() as Text;
     startTime = Time.time;
 }

 // Update once per frame
 void Update()
 {
     minutes = (Time.time - startTime) / 60f;
     seconds = (Time.time - startTime) % 60f;
     counterText.text = string.Format( "{0:00}:{1:00}", minutes, seconds)
 }

Try this script.

 public Text counterText;

     public float seconds, minutes;
     public float time;

     // Initialization
     void Start()
     {
          time = 0;
          counterText = GetComponent<Text>() as Text;
     }

     // Update once per frame
     void Update()
     {
          time += Time.deltaTime;
          minutes = (int)(time / 60f);
          seconds = (int)(time % 60f);
          counterText.text = minutes.ToString("00") + ":" + seconds.ToString("00");
     }
}