C# 时间戳与 标准时间互转

/// <summary>
        /// 获取开停机的时间戳
        /// </summary>
        /// <param name="dtime"></param>
        /// <returns></returns>
        public int getTimeSpan(DateTime dtime)
        {
            //格林威治时间
            //var timeSpan_Greenwich = dtime - new DateTime(1970, 1, 1, 0, 0, 0);
            //标准北京时间
            var timeSpan = dtime - new DateTime(1970, 1, 1, 8, 0, 0);

            //或者这样写北京标准时间
            var timeSpan_beijing = dtime - TimeZone.CurrentTimeZone.ToLocalTime(new DateTime(1970, 1, 1, 0, 0, 0));

           return (int)timeSpan.TotalSeconds;
        }

        /// <summary>  
        /// 时间戳Timestamp转换成日期  
        /// </summary>  
        /// <param name="timeStamp"></param>  
        /// <returns></returns>  
        private DateTime GetDateTime(int timeStamp)
        {
            SaveCommand("timeStamp:" + timeStamp);

            DateTime dtStart = TimeZone.CurrentTimeZone.ToLocalTime(new DateTime(1970, 1, 1));
            long lTime = ((long)timeStamp * 10000000);
            TimeSpan toNow = new TimeSpan(lTime);
            DateTime targetDt = dtStart.Add(toNow);

            if (string.IsNullOrEmpty(targetDt.ToString()))
            {
                targetDt = DateTime.Now;
            }

            SaveCommand("time:" + targetDt.ToString());

            return targetDt;
        }