计算某日期为当年第几周算法

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1，数据库计算

一周是从周日到周六

select DateName(week,getdate())

一周是从周一到周日

set datefirst 1 select DateName(week,getdate())

 

指示一周的第一天的一个整数。可以是下列值之一。

2，c#计算

一周是从周日到周六

 

/// <summary>/// 当前日期为当前年份周数/// </summary>/// <param name="Date">当前时间</param>/// <returns>周数</returns>private int GetWeekOrderOfDate(DateTime Date){//当天所在的年份int year = Date.Year;//当年的第一天DateTime firstDay = new DateTime(year, 1, 1);//当年的第一天是星期几int firstOfWeek = Convert.ToInt32(firstDay.DayOfWeek);//if (firstDay.DayOfWeek == DayOfWeek.Sunday) firstOfWeek = 7;//当年第一周的天数int firstWeekDayNum = 7 - firstOfWeek;//传入日期在当年的天数与第一周天数的差int otherDays = Date.DayOfYear - firstWeekDayNum;//传入日期不在第一周内if (otherDays > 0){int weekNumOfOtherDays;if (otherDays % 7 == 0){weekNumOfOtherDays = otherDays / 7;}else{weekNumOfOtherDays = otherDays / 7 + 1;}return weekNumOfOtherDays + 1;}//传入日期在第一周内else{return 1;}}

 

一周是从周一到周日

/// <summary>/// 当前日期为当前年份周数/// </summary>/// <param name="Date">当前时间</param>/// <returns>周数</returns>private int GetWeekOrderOfDate(DateTime Date){//当天所在的年份int year = Date.Year;//当年的第一天DateTime firstDay = new DateTime(year, 1, 1);//当年的第一天是星期几int firstOfWeek = Convert.ToInt32(firstDay.DayOfWeek);if (firstDay.DayOfWeek == DayOfWeek.Sunday) firstOfWeek = 7;//当年第一周的天数int firstWeekDayNum = 8 - firstOfWeek;//传入日期在当年的天数与第一周天数的差int otherDays = Date.DayOfYear - firstWeekDayNum;//传入日期不在第一周内if (otherDays > 0){int weekNumOfOtherDays;if (otherDays % 7 == 0){weekNumOfOtherDays = otherDays / 7;}else{weekNumOfOtherDays = otherDays / 7 + 1;}return weekNumOfOtherDays + 1;}//传入日期在第一周内else{return 1;}}

 

 

方法2：

public int WeekOfYear(DateTime dt, CultureInfo ci){return ci.Calendar.GetWeekOfYear(dt, ci.DateTimeFormat.CalendarWeekRule, ci.DateTimeFormat.FirstDayOfWeek);}

调用方法  周日到周六算一周
WeekOfYear(Convert.ToDateTime("2012-1-2 00:00:00"),new CultureInfo("zh-CN"))

http://msdn.microsoft.com/zh-cn/library/system.globalization.cultureinfo(VS.80).aspx 

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