C#中关于常用日期的计算

void Main()
{
    DateTime dt = DateTime.Now;  //当前时间

    DateTime startWeek = dt.AddDays( - Convert.ToInt32(dt.DayOfWeek.ToString("d")));  //本周周一
    DateTime endWeek = startWeek.AddDays();//本周周日

    DateTime startMonth = dt.AddDays(-dt.Day);//本月月初
    DateTime endMonth = startMonth.AddMonths().AddDays(-);//本月月末

    DateTime startQuarter = dt.AddMonths( - (dt.Month - ) % ).AddDays( - dt.Day);  //本季度初
    DateTime endQuarter = startQuarter.AddMonths().AddDays(-);  //本季度末

    DateTime startYear = new DateTime(dt.Year, , );  //本年年初
    DateTime endYear = new DateTime(dt.Year, , );  //本年年末

    var startQuarter2 = startYear.AddMonths();//2季度初
    var endQuarter1 = startQuarter2.AddDays(-);//1季度末
    var startQuarter3 = startYear.AddMonths();//3季度初
    var endQuarter2 = startQuarter3.AddDays(-);//2季度末
    var startQuarter4 = startYear.AddMonths();//4季度初
    var endQuarter3 = startQuarter4.AddDays(-);//3季度末

    Console.WriteLine("本周周一：" + startWeek.ToString("yyyy-MM-dd"));
    Console.WriteLine("本周周末：" + endWeek);

    Console.WriteLine("\r\n本月月初：" + startMonth);
    Console.WriteLine("本月月末：" + endMonth);

    Console.WriteLine("\r\n本季度初：" + startQuarter);
    Console.WriteLine("本季度末：" + endQuarter);

    Console.WriteLine("\r\n本年年初：" + startYear);
    Console.WriteLine("本年年末：" + endYear);

    Console.WriteLine("\r\n一季度初：" + startYear);
    Console.WriteLine("一季度末：" + endQuarter1);

    Console.WriteLine("\r\n二季度初：" + startQuarter);
    Console.WriteLine("二季度末：" + endQuarter2);

    Console.WriteLine("\r\n三季度初：" + startQuarter);
    Console.WriteLine("三季度末：" + endQuarter3);

    Console.WriteLine("\r\n四季度初：" + startQuarter);
    Console.WriteLine("四季度末：" + endYear);

    Console.WriteLine();

    System.DateTime startTime = TimeZone.CurrentTimeZone.ToLocalTime( new System.DateTime(, , )); // 当地时区
    long timeStamp = (long)(DateTime.Now - startTime).TotalMilliseconds; // 相差毫秒数

    Console.WriteLine("时间戳：" + timeStamp);

}

结果：

本周周一：--
本周周末：-- ::

本月月初：-- ::
本月月末：-- ::

本季度初：-- ::
本季度末：-- ::

本年年初：-- ::
本年年末：-- ::

一季度初：-- ::
一季度末：-- ::

二季度初：-- ::
二季度末：-- ::

三季度初：-- ::
三季度末：-- ::

四季度初：-- ::
四季度末：-- ::

时间戳：