日期算法

[敢不敢在来一次]

页面上有一个这一年的多少周，代码中怎么算出是这一年的几月几号 到 几月几号 ？

[rencht]

如果是js的话，返回某一年的第几周的第一天的方法^_^：

function getDateByYearAndWeek(year, weeks){
    var date = new Date(year, 0, 1);
    if (weeks == 1)
        return date;
    var weekday = date.getDay();
    var time = date.getTime();
    time += ((weeks - 1) * 7 - weekday) * 24 * 3600000;
    date.setTime(time);
    return date;
}

[ghostkngiht]

        SimpleDateFormat sdf = new SimpleDateFormat("MM dd yyyy");
        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.WEEK_OF_YEAR, 23);
        cal.set(Calendar.DAY_OF_WEEK, 1);
        System.out.println(sdf.format(cal.getTime()));//周日
        cal.set(Calendar.DAY_OF_WEEK, 7);
        System.out.println(sdf.format(cal.getTime()));//周一

[坚持2012]

引用 4 楼 ghostkngiht 的回复:

        SimpleDateFormat sdf = new SimpleDateFormat("MM dd yyyy");
        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.WEEK_OF_YEAR, 23);
        cal.set(Calendar.DAY_OF_WEEK, 1);
        System.out.println(sdf.format(cal.getTime()));//周日
        cal.set(Calendar.DAY_OF_WEEK, 7);
        System.out.println(sdf.format(cal.getTime()));//周一

cal.set(Calendar.WEEK_OF_YEAR, 23);//这个可以设置一个变量，就是你想要的结果，当你输入第几周的时候就会输出周日到周一的日期

[坚持2012]

Scanner sc1=new Scanner(System.in);
		System.out.println("请输入年份:");
		int year=sc1.nextInt();
		Scanner sc=new Scanner(System.in);
		System.out.println("请输入第几周:");
		int week=sc.nextInt();
		SimpleDateFormat sdf = new SimpleDateFormat("MM dd yyyy"); 
		Calendar cal = Calendar.getInstance();
		cal.set(year, 1, 1);
		cal.set(Calendar.WEEK_OF_YEAR, week);        
		cal.set(Calendar.DAY_OF_WEEK, 1);        
		System.out.println(sdf.format(cal.getTime()));//周日       
		cal.set(Calendar.DAY_OF_WEEK, 7);        
		System.out.println(sdf.format(cal.getTime()));//周一

先输入哪一年，然后再输入第几周，就会出现那一年的日期了。

[soton_dolphin]

SimpleDateFormat sdf = new SimpleDateFormat("MM dd yyyy"); Calendar cal = Calendar.getInstance(); cal.set(Calendar.WEEK_OF_YEAR, 23); cal.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY); System.out.println(sdf.format(cal.getTime()));

[无聊找乐]

引用 1 楼 soton_dolphin 的回复:

SimpleDateFormat sdf = new SimpleDateFormat("MM dd yyyy"); Calendar cal = Calendar.getInstance(); cal.set(Calendar.WEEK_OF_YEAR, 23); cal.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY); System.out.println(sdf.format(cal.getTime()));

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