时间转换---- 0000-00-00

public string GetCheckDate()
        {
            var now = DateTime.Now;

            var year = now.Year;       //年
            var month = now.Month;     //月
            var day = now.Day;            //日

            var clock = year + "-";

            if (month < 10)
                clock += "0";

            clock += month + "-";

            if (day < 10)
                clock += "0";

            clock += day + "";

            return (clock);
        }