As3 计算两个日期之间的天数差

/*日期转YYYYMMDD*/

formDate.fullYear+""+(formDate.month<10?("0"+formDate.month):formDate.month)+""+(formDate.day<10?("0"+formDate.day):formDate.day),

/**
* 虽然名字为fromFormatDayStr和toFormatDayStr， 单两个参数所代表的开始和结束年份没有先后顺序；如：
* SelfDateUtil.manyDayNum("20081230", "20110317")与SelfDateUtil.manyDayNum("20110317", "20081230")等效。
* */
private function manyDayNum(fromFormatDayStr:String, toFormatDayStr:String):Number{
var manyAllDayNum:Number = 0; //间隔的天数
var _fromYear:int = int(fromFormatDayStr.substr(0, 4));
var _toYear:int = int(toFormatDayStr.substr(0, 4));
if(_toYear == _fromYear){ //同一年
manyAllDayNum = Number(alreadyOverDay(toFormatDayStr)[0]) - Number(alreadyOverDay(fromFormatDayStr)[0]);
}else if(Math.abs(_toYear - _fromYear) == 1){ //相差一年
if(_toYear > _fromYear){
manyAllDayNum = Number(alreadyOverDay(fromFormatDayStr)[1]) + Number(alreadyOverDay(toFormatDayStr)[0]);
}else{
manyAllDayNum = Number(alreadyOverDay(toFormatDayStr)[1]) + Number(alreadyOverDay(fromFormatDayStr)[0]);
}
}else{ //相差两年或者两年以上
var mangYearNum:Number = Math.abs(Number(_toYear - _fromYear)); //中间间隔的年份
if(_toYear > _fromYear){
manyAllDayNum = Number(alreadyOverDay(fromFormatDayStr)[1]) + Number(alreadyOverDay(toFormatDayStr)[0]);
for(var i:int = 1; i < mangYearNum; i++){
if(isRunYear(String(_fromYear + i))){ //是闰年
manyAllDayNum += 366;
}else{ //不是闰年
manyAllDayNum += 365;
}
}
}else{
manyAllDayNum = Number(alreadyOverDay(toFormatDayStr)[1]) + Number(alreadyOverDay(fromFormatDayStr)[0]);
for(var j:int = 1; j < mangYearNum; j++){
if(isRunYear(String(_toYear + j))){ //是闰年
manyAllDayNum += 366;
}else{ //不是闰年
manyAllDayNum += 365;
}
}
}
}
return manyAllDayNum;
}

/**指定的一年之内已经过了多少天了(算上当天)，
*dayStr标准格式为YYYYMMDD，例如：20100816
*要保证dayStr参数的格式和实际含义正确，如不能出现20100229
*[0]表示已经过了多少天，[1]表示还剩下多少天 */
private function alreadyOverDay(dayFormatStr:String):Array{
var _tempArr:Array = new Array();
var alreadyDayNum:int = 0;
var _year:int = int(dayFormatStr.substr(0, 4));
var _month:int = int(dayFormatStr.substr(4, 2));
var _day:int = int(dayFormatStr.substr(6, 2));
if(_month == 1){
alreadyDayNum = _day;
}else if(_month == 3){
alreadyDayNum = 31 + _day;
}else if(_month == 4){
alreadyDayNum = 62 + _day;
}else if(_month == 5){
alreadyDayNum = 92 + _day;
}else if(_month == 6){
alreadyDayNum = 123 + _day;
}else if(_month == 7){
alreadyDayNum = 153 + _day;
}else if(_month == 8){
alreadyDayNum = 184 + _day;
}else if(_month == 9){
alreadyDayNum = 215 + _day;
}else if(_month == 10){
alreadyDayNum = 245 + _day;
}else if(_month == 11){
alreadyDayNum = 276 + _day;
}else if(_month == 12){
alreadyDayNum = 306 + _day;
}
if(isRunYear(dayFormatStr)){ //是闰年
if(_month == 2){
alreadyDayNum = 31 + _day;
}else if(_month == 1){

}else{
alreadyDayNum += 29;
}
_tempArr[0] = alreadyDayNum; //已经过的天数(算上今天)
_tempArr[1] = 366 - alreadyDayNum; //还剩多少天没有过
}else{ //不是闰年
if(_month == 2){
alreadyDayNum = 31 + _day;
}else if(_month == 1){

}else{
alreadyDayNum += 28;
}
_tempArr[0] = alreadyDayNum; //已经过的天数(算上今天)
_tempArr[1] = 365 - alreadyDayNum; //还剩多少天没有过
}
return _tempArr;
}

/*指定的一年中过了多少天了，dayStr标准格式为YYYYMMDD，例如：20100816*/
private function isRunYear(dayStr:String):Boolean{
var _year:Number = Number(dayStr.substr(0, 4));
if((_year % 4 == 0 && _year % 100 != 0) || _year % 400 == 0){
return true;
}else{
return false;
}
}