时间常用处理

//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);

 

-----SQL------

--本月的天数
select day (dateadd(day,-1,dateadd(month,1,convert(char(8),getdate(),120)+'01')))

--本年的天数
select datediff (day,datename(year,getdate())+'-01-01',datename(year,getdate())+'-12-31')+1

--本月第一天
select convert (char(8),getdate(),120)+'01'

--本月最后一天
select dateadd (day,-1,dateadd(month,1,convert(char(8),getdate(),120)+'01'))
--本月最后一天午夜
select dateadd (ms,-3,dateadd(month,1,convert(char(8),getdate(),120)+'01'))

--本年第一天
select convert (char(5),getdate(),120)+'01-01'
--本年最后一天
select convert (char(5),getdate(),120)+'12-31'
--本年最后一天午夜
select convert (char(5),getdate(),120)+'12-31 23:59:59:997'

--本周一
select dateadd (week,datediff(week,0,getdate()),0)
--本周 星期天
select dateadd (day,-1,dateadd(week,datediff(week,0,getdate())+1,0))
--本周星期天的午夜
select dateadd (ms,-3,dateadd(week,datediff(week,0,getdate())+1,0))

--本季度第一天
select dateadd (quarter,datediff(quarter,0,getdate()),0)
--本季度最后一天
select dateadd (day,-1,dateadd(quarter,datediff(quarter,0,getdate())+1,0))
--本季度最后一天的午夜
select dateadd (ms,-3,dateadd(quarter,datediff(quarter,0,getdate())+1,0))