获取本周的第一天和最后一天的日期知道周数 [英] Get date of first and last day of week knowing week number

问题描述

我需要一周的第一天和最后一天的日期知道周数。

我得到一个开始日期和结束日期，代表在一年中选定的一周的第一天和最后一天。然后，我需要得到上年同周的开始日期和结束日期做一些数据的图形比较。

我设法根据给定的开始日期和结束日期的周数。现在，我需要得到的第一天，上年同周的最后一天的日期。 ？我怎么能做到这一点最快

编辑：这是我得到的周数：

 私人诠释GetWeekNumber（DateTime的日期）
 {
的GregorianCalendar日历=新的GregorianCalendar（GregorianCalendarTypes.USEnglish）; 
返回calendar.GetWeekOfYear（日期，CalendarWeekRule.FirstDay，DayOfWeek.Sunday）; 
} 
  

解决方案

您可以使用以下两种方法计算周数及一个根据给定一年定weeknumber的启动日期

  //该方法是从http://stackoverflow.com/a/11155102/284240 
借公共静态INT GetIso8601WeekOfYear（DateTime的时间）
 {
 DAYOFWEEK天= CultureInfo.InvariantCulture.Calendar.GetDayOfWeek（时间）; 
如果（日> = DayOfWeek.Monday和放大器;和天< = DayOfWeek.Wednesday）
 {
时间= time.AddDays（3）; 
} 
 
返回CultureInfo.InvariantCulture.Calendar.GetWeekOfYear（时间，CalendarWeekRule.FirstFourDayWeek，DayOfWeek.Monday）; 
} 
 
公共静态的DateTime FirstDateOfWeek（年整型，诠释WEEKOFYEAR，System.Globalization.CultureInfo CI）
 {
的DateTime jan1 =新日期时间（年，1， 1）; 
 INT daysOffset =（INT）ci.DateTimeFormat.FirstDayOfWeek  - （INT）jan1.DayOfWeek; 
的DateTime firstWeekDay = jan1.AddDays（daysOffset）; 
 INT firstWeek = ci.Calendar.GetWeekOfYear（jan1，ci.DateTimeFormat.CalendarWeekRule，ci.DateTimeFormat.FirstDayOfWeek）; 
如果（（firstWeek&下; = 1 || firstWeek> = 52）及与放大器; daysOffset> = -3）
 {
 WEEKOFYEAR  -  = 1; 
} 
返回firstWeekDay.AddDays（WEEKOFYEAR * 7）; 
} 
  

然后你就可以得到以下列方式两个日期：

  // 46 
 INT thisWeekNumber = GetIso8601WeekOfYear（DateTime.Today）; 
 // 2013年11月11日
的DateTime Firstdayofweek可= FirstDateOfWeek（2013年，thisWeekNumber，CultureInfo.CurrentCulture）; 
 // 2012年11月12日
的DateTime firstDayOfLastYearWeek = FirstDateOfWeek（2012年，thisWeekNumber，CultureInfo.CurrentCulture）; 
  

...添加6天得到本周结束

I need to get the date of the first and last day of the week knowing the week number.

I get a start date and an end date, representing the first and last day of a selected week in a given year. then I need to get the start date and end date of the same week of the previous year to do a graphical comparison of some data.

I managed to get the week number based on the given start date and end date. Now I need to get the date of the first day and last day of the same week of the previous year. How could I do this quickest ?

EDIT: This is how I got the week number:

 private int GetWeekNumber(DateTime date)
    {
        GregorianCalendar calendar = new GregorianCalendar(GregorianCalendarTypes.USEnglish);
        return calendar.GetWeekOfYear(date, CalendarWeekRule.FirstDay, DayOfWeek.Sunday);            
    }

解决方案

You can use following two methods to calculate the week-number and the start-date of a given weeknumber according to a given year:

// this method is borrowed from http://stackoverflow.com/a/11155102/284240
public static int GetIso8601WeekOfYear(DateTime time)
{
    DayOfWeek day = CultureInfo.InvariantCulture.Calendar.GetDayOfWeek(time);
    if (day >= DayOfWeek.Monday && day <= DayOfWeek.Wednesday)
    {
        time = time.AddDays(3);
    }

    return CultureInfo.InvariantCulture.Calendar.GetWeekOfYear(time, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);
} 

public static DateTime FirstDateOfWeek(int year, int weekOfYear, System.Globalization.CultureInfo ci)
{
    DateTime jan1 = new DateTime(year, 1, 1);
    int daysOffset = (int)ci.DateTimeFormat.FirstDayOfWeek - (int)jan1.DayOfWeek;
    DateTime firstWeekDay = jan1.AddDays(daysOffset);
    int firstWeek = ci.Calendar.GetWeekOfYear(jan1, ci.DateTimeFormat.CalendarWeekRule, ci.DateTimeFormat.FirstDayOfWeek);
    if ((firstWeek <= 1 || firstWeek >= 52) && daysOffset >= -3)
    {
        weekOfYear -= 1;
    }
    return firstWeekDay.AddDays(weekOfYear * 7);
}

Then you can get both dates in the following way:

// 46
int thisWeekNumber = GetIso8601WeekOfYear(DateTime.Today); 
// 11/11/2013  
DateTime firstDayOfWeek= FirstDateOfWeek(2013, thisWeekNumber, CultureInfo.CurrentCulture); 
// 11/12/2012  
DateTime firstDayOfLastYearWeek = FirstDateOfWeek(2012, thisWeekNumber, CultureInfo.CurrentCulture);   

Add 6 days to get the end of the week.

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