//获取日期+时间

DateTime.Now.ToString();            // 2008-9-4 20:02:10
DateTime.Now.ToLocalTime().ToString();        // 2008-9-4 20:12:12

//获取日期

DateTime.Now.ToLongDateString().ToString();    // 2008年9月4日
DateTime.Now.ToShortDateString().ToString();    // 2008-9-4
DateTime.Now.ToString("yyyy-MM-dd");        // 2008-09-04
DateTime.Now.Date.ToString();            // 2008-9-4 0:00:00
//获取时间
DateTime.Now.ToLongTimeString().ToString();    // 20:16:16
DateTime.Now.ToShortTimeString().ToString();    // 20:16
DateTime.Now.ToString("hh:mm:ss");         // 08:05:57
DateTime.Now.TimeOfDay.ToString();         // 20:33:50.7187500

//其他

DateTime.ToFileTime().ToString();        // 128650040212500000
DateTime.Now.ToFileTimeUtc().ToString();    // 128650040772968750
DateTime.Now.ToOADate().ToString();        // 39695.8461709606
DateTime.Now.ToUniversalTime().ToString();    // 2008-9-4 12:19:14

DateTime.Now.Year.ToString();          获取年份    // 2008

DateTime.Now.Month.ToString();      获取月份    // 9
DateTime.Now.DayOfWeek.ToString();  获取星期    // Thursday
DateTime.Now.DayOfYear.ToString();  获取第几天    // 248
DateTime.Now.Hour.ToString();          获取小时    // 20
DateTime.Now.Minute.ToString();     获取分钟    // 31
DateTime.Now.Second.ToString();     获取秒数    // 45

//n为一个数,可以数整数,也可以事小数

dt.AddYears(n).ToString();    //时间加n年
dt.AddDays(n).ToString();    //加n天
dt.AddHours(n).ToString();    //加n小时
dt.AddMonths(n).ToString();    //加n个月
dt.AddSeconds(n).ToString();    //加n秒
dt.AddMinutes(n).ToString();    //加n分