now = new Date();				// now = today's datenewyear = new Date("Dec 31 00:00:00 2000");			// newyear = date of new year 2000
year = now.getFullYear();			// year = this year
year--;						// year = last year newyear.setFullYear(year);			// change newyear to next year
seconds = (now - newyear) / 1000;		//
days = seconds / 60 / 60 / 24;			// calculate week number
weeks = days / 7;				//
weeks = Math.ceil(weeks);
document.write("week number " + weeks + ".");