定时器;如何获取系统时间

using UnityEngine;using System.Collections;public class NewBehaviourScript : MonoBehaviour {    float lastTime;void Start () {        float lastTime = Time.fixedTime;}// Update is called once per framevoid Update () {        float currentTime = Time.fixedTime;        if (currentTime - lastTime > 5.0f)        {            print("定时器");            lastTime = currentTime;        }}}

System.DateTime.Now