Time.timeSinceLevelLoad

static var timeSinceLevelLoad : float

Description

The time this frame has started (Read Only). This is the time in seconds since the last level has been loaded.

JavaScript
    // Sets the gui text to the time it took the player to complete the level
function PlayerCompletedGame() {
guiText.text = Time.timeSinceLevelLoad.ToString();
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
void PlayerCompletedGame() {
guiText.text = Time.timeSinceLevelLoad.ToString();
}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

def PlayerCompletedGame():
guiText.text = Time.timeSinceLevelLoad.ToString()