获取给定日期的正确周数 [英] Get the correct week number of a given date

问题描述

我在谷歌上搜索了很多并找到了很多解决方案，但没有一个给我 2012-12-31 的正确周数.甚至 MSDN 上的示例(link)也失败了.

I have Googled a lot and found a lot of solutions, but none of them give me the correct week number for the 2012-12-31. Even the example on MSDN (link) fails.

2012-12-31 是星期一，因此应该是第 1 周，但我尝试的每种方法都给了我 53.以下是我尝试过的一些方法:

2012-12-31 is Monday, therefore it should be Week 1, but every method I tried gives me 53. Here are some of the methods, that I have tried:

来自 MDSN 库:

DateTimeFormatInfo dfi = DateTimeFormatInfo.CurrentInfo;
Calendar cal = dfi.Calendar;

return cal.GetWeekOfYear(date, dfi.CalendarWeekRule, dfi.FirstDayOfWeek);

解决方案 2:

return new GregorianCalendar(GregorianCalendarTypes.Localized).GetWeekOfYear(date, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);

解决方案 3:

CultureInfo ciCurr = CultureInfo.CurrentCulture;
int weekNum = ciCurr.Calendar.GetWeekOfYear(dtPassed, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);
return weekNum;

更新

当日期为 2012-12-31 时，以下方法实际上返回 1.换句话说，我的问题是我的方法没有遵循 ISO-8601 标准.

The following method actually returns 1 when date is 2012-12-31. In other words, my problem was that my methods were not following the ISO-8601 standard.

// This presumes that weeks start with Monday.
// Week 1 is the 1st week of the year with a Thursday in it.
public static int GetIso8601WeekOfYear(DateTime time)
{
    // Seriously cheat.  If its Monday, Tuesday or Wednesday, then it'll 
    // be the same week# as whatever Thursday, Friday or Saturday are,
    // and we always get those right
    DayOfWeek day = CultureInfo.InvariantCulture.Calendar.GetDayOfWeek(time);
    if (day >= DayOfWeek.Monday && day <= DayOfWeek.Wednesday)
    {
        time = time.AddDays(3);
    }

    // Return the week of our adjusted day
    return CultureInfo.InvariantCulture.Calendar.GetWeekOfYear(time, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);
}

推荐答案

如本MSDN 页面 ISO8601 周和 .Net 周编号略有不同.

As noted in this MSDN page there is a slight difference between ISO8601 week and .Net week numbering.

您可以参考 MSDN 博客中的这篇文章以获得更好的解释:Microsoft .Net 中的 ISO 8601 年度周格式"

You can refer to this article in MSDN Blog for a better explanation: "ISO 8601 Week of Year format in Microsoft .Net"

简而言之，.Net 允许将数周拆分为数年，而 ISO 标准则不允许.文章中还有一个简单的函数可以获取一年中最后一周的正确 ISO 8601 周数.

Simply put, .Net allow weeks to be split across years while the ISO standard does not. In the article there is also a simple function to get the correct ISO 8601 week number for the last week of the year.

更新以下方法实际上为 2012-12-31 返回 1，这在 ISO 8601(例如德国)中是正确的.

Update The following method actually returns 1 for 2012-12-31 which is correct in ISO 8601 (e.g. Germany).

// This presumes that weeks start with Monday.
// Week 1 is the 1st week of the year with a Thursday in it.
public static int GetIso8601WeekOfYear(DateTime time)
{
    // Seriously cheat.  If its Monday, Tuesday or Wednesday, then it'll 
    // be the same week# as whatever Thursday, Friday or Saturday are,
    // and we always get those right
    DayOfWeek day = CultureInfo.InvariantCulture.Calendar.GetDayOfWeek(time);
    if (day >= DayOfWeek.Monday && day <= DayOfWeek.Wednesday)
    {
        time = time.AddDays(3);
    }

    // Return the week of our adjusted day
    return CultureInfo.InvariantCulture.Calendar.GetWeekOfYear(time, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);
} 

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