C# 根据年、月、周、星期获得日期等

原文: C# 根据年、月、周、星期获得日期等

[参考]

http://blog.csdn.net/livening/article/details/6049341

http://zhidao.baidu.com/question/378600365.html

http://www.cnblogs.com/roy117/archive/2008/03/25/1121584.html

 

楼上几层的代码都太多了，不用那么复杂。

先跟你说一下原理：

1.国际上的WeekDay是从周日到周六的顺序

2.再说C#的DayOfWeek枚举值是依次从0到6，即周一的枚举值为1

3.算法规律：非周一的就要去获取上周一，而一周有7天。以周一为分界点，当天为周二及往后，则算法为减7天后再减当天N数再加1；周日的话，算法为减7天后再加1。

以此算法规律，可建立获取任意指定日期的上周几的日期的通用方法，代码如下：

pubilc DateTime getWeekUpOfDate(DateTime dt,DayOfWeek weekday,int Number)

{

    int wd1=(int)weekday;

    int wd2=(int)dt.DayOfWeek;

    return wd2==wd1?dt.AddDay(7*Number):dt.AddDay(7*Number-wd2+wd1);

}

参数说明：dt为指定的以哪个日期来计算，weekday为计算（上、当前、下）几周的周几

方法调用如下：

DateTime dt=getWeekUpOfDate(DateTime.Now,DayOfWeek.Monday,-1);

这是获取当前日期的上周一的日期

DateTime dt=getWeekUpOfDate(DateTime.Now,DayOfWeek.Monday,-2);

这是获取当前日期的上上周一的日期

DateTime dt=getWeekUpOfDate(DateTime.Now,DayOfWeek.Monday,1);

这是获取当前日期的下周一的日期

DateTime dt=getWeekUpOfDate(DateTime.Now,DayOfWeek.Monday,0);

这是获取本周周一的日期

/// <summary>   

　　/// 取得某月的第一天   

/// </summary>
/// <param name="datetime">要取得月份第一天的时间</param>
/// <returns></returns>
private DateTime FirstDayOfMonth(DateTime datetime)
{
    return datetime.AddDays(1 - datetime.Day);
}

/**//// <summary>
/// 取得某月的最后一天
/// </summary>
/// <param name="datetime">要取得月份最后一天的时间</param>
/// <returns></returns>
private DateTime LastDayOfMonth(DateTime datetime)

    return datetime.AddDays(1 - datetime.Day).AddMonths(1).AddDays(-1);
}

/**//// <summary>
/// 取得上个月第一天
/// </summary>
/// <param name="datetime">要取得上个月第一天的当前时间</param>
/// <returns></returns>
private DateTime FirstDayOfPreviousMonth(DateTime datetime)
{
    return datetime.AddDays(1 - datetime.Day).AddMonths(-1);
}

/**//// <summary>
/// 取得上个月的最后一天
/// </summary>
/// <param name="datetime">要取得上个月最后一天的当前时间</param>
/// <returns></returns>
private DateTime LastDayOfPrdviousMonth(DateTime datetime)
{
    return datetime.AddDays(1 - datetime.Day).AddDays(-1);
}

/// <summary> /// 取得某月的第一天 /// </summary> /// <param name="datetime">要取得月份第一天的时间</param> /// <returns></returns> private DateTime FirstDayOfMonth(DateTime datetime) { return datetime.AddDays(1 - datetime.Day); } /**//// <summary> /// 取得某月的最后一天 /// </summary> /// <param name="datetime">要取得月份最后一天的时间</param> /// <returns></returns> private DateTime LastDayOfMonth(DateTime datetime) { return datetime.AddDays(1 - datetime.Day).AddMonths(1).AddDays(-1); } /**//// <summary> /// 取得上个月第一天 /// </summary> /// <param name="datetime">要取得上个月第一天的当前时间</param> /// <returns></returns> private DateTime FirstDayOfPreviousMonth(DateTime datetime) { return datetime.AddDays(1 - datetime.Day).AddMonths(-1); } /**//// <summary> /// 取得上个月的最后一天 /// </summary> /// <param name="datetime">要取得上个月最后一天的当前时间</param> /// <returns></returns> private DateTime LastDayOfPrdviousMonth(DateTime datetime) { return datetime.AddDays(1 - datetime.Day).AddDays(-1); }

 

 

C# DateTime 日期加1天 减一天 加一月 减一月 等方法

[c-sharp] view plain copy print ?

//今天
DateTime.Now.Date.ToShortDateString();
//昨天，就是今天的日期减一
DateTime.Now.AddDays(-1).ToShortDateString();
//明天，同理，加一
DateTime.Now.AddDays(1).ToShortDateString();

//本周(要知道本周的第一天就得先知道今天是星期几，从而得知本周的第一天就是几天前的那一天，要注意的是这里的每一周是从周日始至周六止
DateTime.Now.AddDays(Convert.ToDouble((0 - Convert.ToInt16(DateTime.Now.DayOfWeek)))).ToShortDateString();
DateTime.Now.AddDays(Convert.ToDouble((6 - Convert.ToInt16(DateTime.Now.DayOfWeek)))).ToShortDateString();
//如果你还不明白，再看一下中文显示星期几的方法就应该懂了
//由于DayOfWeek返回的是数字的星期几，我们要把它转换成汉字方便我们阅读，有些人可能会用switch来一个一个地对照，其实不用那么麻烦的
string[] Day = new string[] { "星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六" };
Day[Convert.ToInt16(DateTime.Now.DayOfWeek)];

//上周，同理，一个周是7天，上周就是本周再减去7天，下周也是一样
DateTime.Now.AddDays(Convert.ToDouble((0 - Convert.ToInt16(DateTime.Now.DayOfWeek))) - 7).ToShortDateString();
DateTime.Now.AddDays(Convert.ToDouble((6 - Convert.ToInt16(DateTime.Now.DayOfWeek))) - 7).ToShortDateString();
//下周
DateTime.Now.AddDays(Convert.ToDouble((0 - Convert.ToInt16(DateTime.Now.DayOfWeek))) + 7).ToShortDateString();
DateTime.Now.AddDays(Convert.ToDouble((6 - Convert.ToInt16(DateTime.Now.DayOfWeek))) + 7).ToShortDateString();
//本月,很多人都会说本月的第一天嘛肯定是1号，最后一天就是下个月一号再减一天。当然这是对的
//一般的写法
DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString() + "1"; //第一天
DateTime.Parse(DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString() + "1").AddMonths(1).AddDays(-1).ToShortDateString();//最后一天

//巧用C#里ToString的字符格式化更简便
DateTime.Now.ToString("yyyy-MM-01");
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(1).AddDays(-1).ToShortDateString();

//上个月，减去一个月份
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(-1).ToShortDateString();
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
//下个月，加去一个月份
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(1).ToShortDateString();
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(2).AddDays(-1).ToShortDateString();
//7天后
DateTime.Now.Date.ToShortDateString();
DateTime.Now.AddDays(7).ToShortDateString();
//7天前
DateTime.Now.AddDays(-7).ToShortDateString();
DateTime.Now.Date.ToShortDateString();

//本年度，用ToString的字符格式化我们也很容易地算出本年度的第一天和最后一天
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).ToShortDateString();
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(1).AddDays(-1).ToShortDateString();
//上年度，不用再解释了吧
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(-1).ToShortDateString();
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddDays(-1).ToShortDateString();
//下年度
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(1).ToShortDateString();
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(2).AddDays(-1).ToShortDateString();

//本季度，很多人都会觉得这里难点，需要写个长长的过程来判断。其实不用的，我们都知道一年四个季度，一个季度三个月
//首先我们先把日期推到本季度第一个月，然后这个月的第一天就是本季度的第一天了
DateTime.Now.AddMonths(0 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01");
//同理，本季度的最后一天就是下季度的第一天减一
DateTime.Parse(DateTime.Now.AddMonths(3 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
//下季度，相信你们都知道了。。。。收工
DateTime.Now.AddMonths(3 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01");
DateTime.Parse(DateTime.Now.AddMonths(6 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
//上季度
DateTime.Now.AddMonths(-3 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01");
DateTime.Parse(DateTime.Now.AddMonths(0 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
 c# 根据日期获取星期方法 
     
       protected void Page_Load(object sender, EventArgs e) 
          { 
              int m = System.DateTime.Today.Month; 
              int y = System.DateTime.Today.Year; 
              int d = System.DateTime.Today.Day; 
              int weeks = getWeekDay(y, m, d); 
              switch (weeks) 
              { 
                  case 1: 
                      this.TextBox1.Text = "星期一"; 
                      break; 
                  case 2: 
                      this.TextBox1.Text = "星期二"; 
                      break; 
                  case 3: 
                      this.TextBox1.Text = "星期三"; 
                      break; 
                  case 4: 
                      this.TextBox1.Text = "星期四"; 
                      break; 
                  case 5: 
                      this.TextBox1.Text = "星期五"; 
                      break; 
                  case 6: 
                      this.TextBox1.Text = "星期六"; 
                      break; 
                  case 7: 
                      this.TextBox1.Text = "星期日"; 
                      break; 
              } 
              
              
          } 
        
          /// <summary>根据日期，获得星期几</summary>    /// <param name="y">年</param>     /// <param name="m">月</param>     /// <param name="d">日</param>     /// <returns>星期几，1代表星期一；7代表星期日</returns>    public static int getWeekDay(int y, int m, int d)    {        if (m == 1) m = 13;        if (m == 2) m = 14;        int week = (d + 2 * m + 3 * (m + 1) / 5 + y + y / 4 - y / 100 + y / 400) % 7 + 1;        return week;    }
 
      
        
      C# 根据年、月、周、星期获得日期等 
        
       
        
         
          
           
            
            /// <summary>
/// 取指定日期是一年中的第几周
/// </summary>
/// <param name="dtime">给定的日期</param>
/// <returns>数字 一年中的第几周</returns>
public static int WeekOfYear(DateTime dtime)
{
    try
    {
        //确定此时间在一年中的位置
        int dayOfYear = dtime.DayOfYear;
        //当年第一天
        DateTime tempDate = new DateTime(dtime.Year, 1, 1);
        //确定当年第一天
        int tempDayOfWeek = (int)tempDate.DayOfWeek;
        tempDayOfWeek = tempDayOfWeek == 0 ? 7 : tempDayOfWeek;
        ////确定星期几
        int index = (int)dtime.DayOfWeek;
        index = index == 0 ? 7 : index;

        //当前周的范围
        DateTime retStartDay = dtime.AddDays(-(index - 1));
        DateTime retEndDay = dtime.AddDays(6 - index);

        //确定当前是第几周
        int weekIndex = (int)Math.Ceiling(((double)dayOfYear + tempDayOfWeek - 1) / 7);

        if (retStartDay.Year < retEndDay.Year)
        {
            weekIndex = 1;
        }

        return weekIndex;
    }
    catch (Exception ex)
    {
        throw new Exception(ex.Message);
    }

}

/// <summary>
/// 求某年有多少周
/// </summary>
/// <param name="dtime"></param>
/// <returns></returns>
public static int GetWeekOfYear(DateTime dtime)
{
    int countDay = DateTime.Parse(dtime.Year + "-12-31").DayOfYear;
    int countWeek = countDay / 7;
    return countWeek;
}


//根据年月日获得星期几
public static string CaculateWeekDay(int month, int day)
{
    string weekstr = string.Empty;
    int year = DateTime.Now.Year;
    //把一月和二月看成是上一年的十三月和十四月
    if (month == 1) { month = 13; year--; }
    if (month == 2) { month = 14; year--; }
    int week = (day + 2 * month + 3 * (month + 1) / 5 + year + year / 4 - year / 100 + year / 400) % 7;
    switch (week)
    {
        case 0: weekstr = "1"; break;
        case 1: weekstr = "2"; break;
        case 2: weekstr = "3"; break;
        case 3: weekstr = "4"; break;
        case 4: weekstr = "5"; break;
        case 5: weekstr = "6"; break;
        case 6: weekstr = "7"; break;
    }
    return weekstr;
}

/// <summary>
/// 根据2个时间段获得相应的周数
/// </summary>
/// <param name="beginDate"></param>
/// <param name="endDate"></param>
/// <returns></returns>
public static int WeekOfDate(DateTime beginDate, DateTime endDate)
{
    TimeSpan ts1 = new TimeSpan(beginDate.Ticks);
    TimeSpan ts2 = new TimeSpan(endDate.Ticks);
    TimeSpan ts = ts2.Subtract(ts1).Duration();
    int weeks = ts.Days / 7;

    //确定此时间在一年中的位置
    int dayOfYear = beginDate.DayOfYear;
    //当年第一天
    DateTime tempDate = new DateTime(beginDate.Year, beginDate.Month, beginDate.Day);
    //最后一天
    DateTime tempendDate = new DateTime(endDate.Year, endDate.Month, endDate.Day);
    int tempDayOfWeek = (int)tempDate.DayOfWeek;
    tempDayOfWeek = tempDayOfWeek == 0 ? 7 : tempDayOfWeek;

    ////确定星期几
    int startindex = (int)beginDate.DayOfWeek;
    startindex = startindex == 0 ? 7 : startindex;
    //当前周的范围
    DateTime retStartDay = beginDate.AddDays(-(startindex - 1));
    DateTime retEndDay = beginDate.AddDays(7 - startindex);
    //确定当前是第几周
    int weekIndex = (int)Math.Ceiling(((double)dayOfYear + tempDayOfWeek - 1) / 7);

    return weeks;
}

/// <summary>
/// 根据起始时间，获取第几周
/// </summary>
/// <param name="dtime">当前时间</param>
/// <returns></returns>
public static int WeekOfTermDate(DateTime dtime)
{
    string datetime = "2011-3-1";

    TimeSpan ts1 = new TimeSpan(dtime.Ticks);
    TimeSpan ts2 = new TimeSpan(Convert.ToDateTime(datetime).Ticks);
    TimeSpan ts = ts2.Subtract(ts1).Duration();

    //确定此时间在一年中的位置
    int dayOfYear = ts.Days;
    //当年第一天
    DateTime tempDate = new DateTime(Convert.ToDateTime(datetime).Year, Convert.ToDateTime(datetime).Month, Convert.ToDateTime(datetime).Day);

    int tempDayOfWeek = (int)tempDate.DayOfWeek;
    tempDayOfWeek = tempDayOfWeek == 0 ? 7 : tempDayOfWeek;
    ////确定星期几
    int index = (int)dtime.DayOfWeek;
    index = index == 0 ? 7 : index;

    //当前周的范围
    DateTime retStartDay = dtime.AddDays(-(index - 1));
    DateTime retEndDay = dtime.AddDays(7 - index);

    //确定当前是第几周
    int weekIndex = (int)Math.Ceiling(((double)dayOfYear + tempDayOfWeek) / 7);
    return weekIndex;
}

/// <summary>
/// 根据周，星期获得具体年月日
/// </summary>
/// <param name="week">第几周</param>
/// <param name="day">星期几</param>
/// <returns></returns>
public static DateTime DateTimeByWeekAndDay(int week, int day)
{
    DateTime someTime = Convert.ToDateTime("2011-3-1");

    int i = someTime.DayOfWeek - DayOfWeek.Monday;
    if (i == -1) i = 6;// i值 > = 0 ，因为枚举原因，Sunday排在最前，此时Sunday-Monday=-1，必须+7=6。
    TimeSpan ts = new TimeSpan(i, 0, 0, 0);

    //获取第N周的星期一
    someTime = someTime.Subtract(ts).AddDays((week - 1) * 7);
    //获得星期几
    someTime = someTime.AddDays(day - 1);
    return someTime;
} 
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
          
         
        
       
        
      private static int GetWeekOfYear()   {            //一.找到第一周的最后一天（先获取1月1日是星期几，从而得知第一周周末是几）            int firstWeekend=7-Convert.ToInt32(DateTime.Parse(DateTime.Today.Year + "-1-1").DayOfWeek);                        //二.获取今天是一年当中的第几天            int currentDay = DateTime.Today.DayOfYear; 
                  //三.（今天 减去 第一周周末）/7 等于 距第一周有多少周 再加上第一周的1 就是今天是今年的第几周了            //    刚好考虑了惟一的特殊情况就是，今天刚好在第一周内，那么距第一周就是0 再加上第一周的1 最后还是1            return Convert.ToInt32(Math.Ceiling((currentDay - firstWeekend) / 7.0)) + 1;     }