javascrip date

/**
 * 获取指定时间年的最后一天
 * @param now 指定时间 Date 对象
 * @return Date 某年的最后一天
 */
ZCPGFFutil.getLastDayInYear = function(now){
	var nextyear = now.getFullYear()+1;
	var nowLast = new Date(nextyear,0,1) - 1000*60*60*24;
	return nowLast;
};

/**
 * 
 * 求一日期到今年最后一天之间间隔的天数
 * @return number
 * 
 */
ZCPGFFutil.getDateNumber = function(date){
	var lastDay = ZCPGFFutil.getLastDayInYear(date);
	return parseInt(Math.abs(new Date(lastDay)-date)/1000/24/60/60);
}

/**
 * 日期格式化
 * @return yyyy - mm - dd 
 */
Date.prototype.format = function(){
	var str = "";
	var year = this.getFullYear();
	var month = this.getMonth() + 1;
	if(month < 10){
		month = "0" + month;
	}
	var day = this.getDate();
	if(day < 10){
		day = "0" + day;
	}
	str = year + " - " + month + " - " + day;
	return str;
};