使用指定格式的字符串变量格式化日期字符串

 private void btn_GetTime_Click(object sender, EventArgs e)
        {
            lab_time.Text =
                DateTime.Now.ToString("d") + "\n" +//使用指定格式的字符串变量格式化日期字符串
                DateTime.Now.ToString("D") + "\n" +
                DateTime.Now.ToString("f") + "\n" +
                DateTime.Now.ToString("F") + "\n" +
                DateTime.Now.ToString("g") + "\n" +
                DateTime.Now.ToString("G") + "\n" +
                DateTime.Now.ToString("R") + "\n" +
                DateTime.Now.ToString("y") + "\n" +
                "当前系统时间为："+DateTime.Now.ToString(//使用自定义格式格式化字符串
                "yyyy年MM月dd日 HH时mm分ss秒");
        }

 private void btn_Get_Click(object sender, EventArgs e)
        {
            MessageBox.Show("间隔 "+
                DateAndTime.DateDiff(//使用DateDiff方法获取日期间隔
                DateInterval.Day, dtpicker_first.Value, dtpicker_second.Value,
                FirstDayOfWeek.Sunday, FirstWeekOfYear.Jan1).ToString()+" 天", "间隔时间");

        }