正月から何週目かを調べる

/**
 * Copyright _wonder ( http://wonderfl.net/user/_wonder )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/wQfS
 */

package {
    import flash.display.Sprite;
    import flash.text.TextField;
    
    public class FlashTest extends Sprite {
        public function FlashTest() {
            var txt:TextField = new TextField();
            var nowdate:Date = new Date();
            var yeardate:Date = new Date( nowdate.getFullYear(), 0, 1 );
            var diffDays:Number = Math.ceil((nowdate.getTime() - yeardate.getTime()) / (24 * 60 * 60 * 1000));
            var supDays:Number = yeardate.getDay()+1;
            
            var weekNum:Number = Math.ceil((diffDays+supDays)/7);
            txt.text = String(weekNum);
            addChild( txt );
        }
    }
}