//以下的毫秒都采用最大997，而不是999 因为SQL SERVER的精度为3毫秒
            //本月的天数
            int daysInMonth = DateTime.DaysInMonth(DateTime.Now.Year, DateTime.Now.Month);

            //本年的天数 是否是闰年           
            int daysInYear = DateTime.IsLeapYear(DateTime.Now.Year) ? 366 : 365;

            //本月第一天
            DateTime firstDayInMonth = new DateTime(DateTime.Now.Year, DateTime.Now.Month, 1);
            //本月的最后一天 本月1号加一个月得下月1号，再剪掉一天就是本月最后一天
            DateTime lastDayInMonth = new DateTime(DateTime.Now.Year, DateTime.Now.Month, 1).AddMonths(1).AddDays(-1);
            //本月最后一天的午夜
            DateTime lastDayInMonth2 = new DateTime(DateTime.Now.Year, DateTime.Now.Month, 1).AddMonths(1).AddMilliseconds(-3);

            //本年第一天
            DateTime firstDayInYear = new DateTime(DateTime.Now.Year, 1, 1);
            
            //本年最后一天
            DateTime lastDayInYear = new DateTime(DateTime.Now.Year, 12, 31);
            //本年最后一天的午夜
            DateTime lastDayInYear2 = new DateTime(DateTime.Now.Year, 12, 31, 23, 59, 59, 997);

            //得到星期几 星期天为7
            int dayOfWeek = Convert.ToInt32(DateTime.Now.DayOfWeek) < 1 ? 7 : Convert.ToInt32(DateTime.Now.DayOfWeek);
            //本周一
            DateTime monday = new DateTime(DateTime.Now.Year,DateTime.Now.Month,DateTime.Now.Day).AddDays(1 - dayOfWeek);
            //本周 星期天
            DateTime sunday = monday.AddDays(6);
            //本周 星期天的午夜
            DateTime sunday2 = monday.AddDays(7).AddMilliseconds(-3);

            //本季度第一天
            DateTime firsyDayInQuarter = new DateTime(DateTime.Now.Year, DateTime.Now.Month - (DateTime.Now.Month - 1) % 3, 1);
            //本季度最后一天
            DateTime lastDayInQuarter = firsyDayInQuarter.AddMonths(3).AddDays(-1);
            //本季度最后一天的午夜
            DateTime lastDayInQuarter2 = firsyDayInQuarter.AddMonths(3).AddMilliseconds(-3);


//csharp/824