C# 根据年、月、周、星期获得日期等

时间：2021-05-19 06:35:24

原文:C# 根据年、月、周、星期获得日期等

　　/// 取得某月的第一天

  1. /// </summary>
  2. /// <param name="datetime">要取得月份第一天的时间</param>
  3. /// <returns></returns>
  4. private DateTime FirstDayOfMonth(DateTime datetime)
  5. {
  6. return datetime.AddDays(1 - datetime.Day);
  7. }
  8. /**//// <summary>
  9. /// 取得某月的最后一天
  10. /// </summary>
  11. /// <param name="datetime">要取得月份最后一天的时间</param>
  12. /// <returns></returns>
  13. private DateTime LastDayOfMonth(DateTime datetime)
  14. return datetime.AddDays(1 - datetime.Day).AddMonths(1).AddDays(-1);
  15. }
  16. /**//// <summary>
  17. /// 取得上个月第一天
  18. /// </summary>
  19. /// <param name="datetime">要取得上个月第一天的当前时间</param>
  20. /// <returns></returns>
  21. private DateTime FirstDayOfPreviousMonth(DateTime datetime)
  22. {
  23. return datetime.AddDays(1 - datetime.Day).AddMonths(-1);
  24. }
  25. /**//// <summary>
  26. /// 取得上个月的最后一天
  27. /// </summary>
  28. /// <param name="datetime">要取得上个月最后一天的当前时间</param>
  29. /// <returns></returns>
  30. private DateTime LastDayOfPrdviousMonth(DateTime datetime)
  31. {
  32. return datetime.AddDays(1 - datetime.Day).AddDays(-1);
  33. }

/// <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

  1. //今天
  2. DateTime.Now.Date.ToShortDateString();
  3. //昨天，就是今天的日期减一
  4. DateTime.Now.AddDays(-1).ToShortDateString();
  5. //明天，同理，加一
  6. DateTime.Now.AddDays(1).ToShortDateString();
  7. //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
  8. DateTime.Now.AddDays(Convert.ToDouble((0 - Convert.ToInt16(DateTime.Now.DayOfWeek)))).ToShortDateString();
  9. DateTime.Now.AddDays(Convert.ToDouble((6 - Convert.ToInt16(DateTime.Now.DayOfWeek)))).ToShortDateString();
  10. //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
  11. //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
  12. 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" };
  13. Day[Convert.ToInt16(DateTime.Now.DayOfWeek)];
  14. //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
  15. DateTime.Now.AddDays(Convert.ToDouble((0 - Convert.ToInt16(DateTime.Now.DayOfWeek))) - 7).ToShortDateString();
  16. DateTime.Now.AddDays(Convert.ToDouble((6 - Convert.ToInt16(DateTime.Now.DayOfWeek))) - 7).ToShortDateString();
  17. //下周
  18. DateTime.Now.AddDays(Convert.ToDouble((0 - Convert.ToInt16(DateTime.Now.DayOfWeek))) + 7).ToShortDateString();
  19. DateTime.Now.AddDays(Convert.ToDouble((6 - Convert.ToInt16(DateTime.Now.DayOfWeek))) + 7).ToShortDateString();
  20. //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
  21. //一般的写法
  22. DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString() + "1"; //第一天
  23. DateTime.Parse(DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString() + "1").AddMonths(1).AddDays(-1).ToShortDateString();//最后一天
  24. //巧用C#里ToString的字符格式化更简便
  25. DateTime.Now.ToString("yyyy-MM-01");
  26. DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(1).AddDays(-1).ToShortDateString();
  27. //上个月，减去一个月份
  28. DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(-1).ToShortDateString();
  29. DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
  30. //下个月，加去一个月份
  31. DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(1).ToShortDateString();
  32. DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(2).AddDays(-1).ToShortDateString();
  33. //7天后
  34. DateTime.Now.Date.ToShortDateString();
  35. DateTime.Now.AddDays(7).ToShortDateString();
  36. //7天前
  37. DateTime.Now.AddDays(-7).ToShortDateString();
  38. DateTime.Now.Date.ToShortDateString();
  39. //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
  40. DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).ToShortDateString();
  41. DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(1).AddDays(-1).ToShortDateString();
  42. //上年度，不用再解释了吧
  43. DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(-1).ToShortDateString();
  44. DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddDays(-1).ToShortDateString();
  45. //下年度
  46. DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(1).ToShortDateString();
  47. DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(2).AddDays(-1).ToShortDateString();
  48. //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
  49. //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
  50. DateTime.Now.AddMonths(0 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01");
  51. //同理，本季度的最后一天就是下季度的第一天减一
  52. DateTime.Parse(DateTime.Now.AddMonths(3 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
  53. //下季度，相信你们都知道了。。。。收工
  54. DateTime.Now.AddMonths(3 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01");
  55. DateTime.Parse(DateTime.Now.AddMonths(6 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
  56. //上季度
  57. DateTime.Now.AddMonths(-3 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01");
  58. DateTime.Parse(DateTime.Now.AddMonths(0 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();

  59. 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;
        }

  60. 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;
         }

     

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