week2.js - What the hell are you doing?

myModify = document.lastModified;

myD = new Date(myModify);
myYear = myD.getYear();
myYear4 = (myYear < 2000) ? myYear+1900 : myYear;
myMonth = myD.getMonth() + 1;
myDate = myD.getDate();
myDay = myD.getDay();

monthdays = new Array(31,28,31,30,31,30,31,31,30,31,30,31);

if(((myYear%4==0)&&(myYear%100==0))||(myYear%400==0)){
	monthdays[1]=29;
}

myStr = myMonth+"月"+myDate+"日";

days = myDate - 6;

if (days>0){
	myStr2 = myMonth + "月" + days + "日";	
}else{
	newMonth = myMonth - 1;
	a = monthdays[myMonth];
	b = a + days;
	myStr2 = newMonth + "月" + b + "日";
}

if(newMonth=0){
	b = 31 + days;
	myStr2 =  "12月" + b + "日";
}

document.write( myStr2+"～"+myStr );