如何判断一个时间为当年的第几周?

[gang2yan]

比如： 时间：2010-08-19 为当年的第几周？

[whycom]

dayofyear/7

[haichunz]

dt = DateTime.Today.DayOfWeek.ToString();

[Peter200694013]

DateTime dt = DateTime.Now;

Console.WriteLine(dt.DayOfYear/7);

[堆代码的爱因斯坦]

http://blog.csdn.net/rubbish_only/archive/2006/09/21/1204520.aspx
参考

[porschev]

[Quote=引用 1 楼 whycom 的回复:]
dayofyear/7
[/Quote]

+1

[q107770540]

  private int DatePart(System.DateTime dt)
        {
            int weeknow = Convert.ToInt32(dt.DayOfWeek);//今天星期几
            int daydiff = (-1) * (weeknow + 1);//今日与上周末的天数差
            int days = System.DateTime.Now.AddDays(daydiff).DayOfYear;//上周末是本年第几天
            int weeks = days / 7;
            if (days % 7 != 0)
            {
                weeks++;
            }
            //此时，weeks为上周是本年的第几周
            return (weeks + 1);
        }


    DateTime dt = Convert.ToDateTime("2010-08-19");
            
            Response.Write(DatePart(dt).ToString());  //结果：34

[zengbingling]

dayofyear / 7 + (dayofyear % 7) > 0 ? 1 : 0;

[wuyq11]

public int Weekofyear(DateTime dtime)
{
int weeknum = 1; //默认的周数从1开始
DateTime firstdate = DateTime.Parse(dtime.Year.ToString() + "-1" + "-1");
DayOfWeek firstweek = firstdate .DayOfWeek;
for (int i = (int)firstweek + 1; i <= dtime.DayOfYear; i = i + 7)
{
weeknum = weeknum + 1;
}
return weeknum ;
}
时间范围

[阿双2009]

            //目标日期
            DateTime dt = DateTime.Now;

            //该年1月1日所在的周，定义为第一周，sunday为0，monday为1
            DateTime dtFirst = new DateTime(dt.Year, 1, 1);

            //目标日期距离第一天的天数
            int daysCount = Convert.ToInt32((dt - dtFirst).TotalDays);

            //将第一天的日期补齐
            daysCount += Convert.ToInt32(dtFirst.DayOfWeek);

            //目标日期所在的周
            int weeksCount = daysCount / 7;

            //目标日期所在的天
            int dayIdx = Convert.ToInt32(dt.DayOfWeek);

            //显示结果
            Console.WriteLine("日期" + dt.ToShortDateString() + "是第" + (weeksCount + 1).ToString() + "周的第" + dayIdx.ToString() + "天。");