//可接受的公历日期范围是2001-1-1至2050-12-31

//数组LunarDaysOfMonth存入农历2001年到2050年每年中的月天数信息
//农历每月只能是29或30天，一年用12(或13)个二进制位表示，从高到低，对应位为1表示30天，否则29天
var LunarDaysOfMonth = new Array(0xd4a8, 0xd4a0, 0xda50, 0x5aa8, 0x56a0, 0xaad8, 0x25d0, 0x92d0, 0xc958, 0xa950, 0xb4a0, 0xb550, 0xb550, 0x55a8, 0x4ba0, 0xa5b0, 0x52b8, 0x52b0, 0xa930, 0x74a8, 0x6aa0, 0xad50, 0x4da8, 0x4b60, 0x9570, 0xa4e0, 0xd260, 0xe930, 0xd530, 0x5aa0, 0x6b50, 0x96d0, 0x4ae8, 0x4ad0, 0xa4d0, 0xd258, 0xd250, 0xd520, 0xdaa0, 0xb5a0, 0x56d0, 0x4ad8, 0x49b0, 0xa4b8, 0xa4b0, 0xaa50, 0xb528, 0x6d20, 0xada0, 0x55b0);
//数组LunarLeapYear存放农历2001年到2050年闰月的月份，如没有则为0，从高到低，每字节存两年
var LunarLeapYear = new Array(0x40, 0x02, 0x07, 0x00, 0x50, 0x04, 0x09, 0x00, 0x60, 0x04, 0x00, 0x20, 0x60, 0x05, 0x00, 0x30, 0xb0, 0x06, 0x00, 0x50, 0x02, 0x07, 0x00, 0x50, 0x03);

//返回农历iLunarYear年的闰月月份，如没有则返回0
function GetLeapMonth(iLunarYear)
{
	var Leap = LunarLeapYear[(iLunarYear - 2001) >> 1];
	return (((iLunarYear - 2001) & 1) == 0) ? (Leap >> 4) : (Leap & 0x0f);
}
//返回农历iLunarYer年iLunarMonth月的天数，结果是一个长整数
//如果iLunarMonth不是闰月，高字为0，低字为该月的天数
//如果iLunarMonth是闰月，高字为后一个月的天数，低字为前一个月的天数
function LunarMonthDays(iLunarYear, iLunarMonth)
{
	var High;
	var Low;
	var Bit;
	High = 0;
	Low = 29;
	Bit = 16 - iLunarMonth;
	if ((iLunarMonth > GetLeapMonth(iLunarYear)) && (GetLeapMonth(iLunarYear) > 0))  Bit--;
	if ((LunarDaysOfMonth[iLunarYear - 2001] & (1 << Bit)) > 0)  Low++;
	if (iLunarMonth == GetLeapMonth(iLunarYear))
	{
		High = ((LunarDaysOfMonth[iLunarYear - 2001] & (1 << (Bit-1))) > 0) ?  30 : 29;
	}
	return Low + (High << 16);
}

//返回农历iLunarYear年的总天数
function LunarYearDays(iLunarYear)
{
	var Days;
	var tmp;
	Days = 0;
	for (var i=1; i <= 12; i++)
	{
		tmp = LunarMonthDays(iLunarYear, i);
		Days = Days + ((tmp >> 16) & 0xffff);//取高位
		Days = Days + (tmp & 0xffff);//取低位
	}
	return Days;
}

//将农历iLunarYear年格式化成天干地支记年法表示的字符串
function FormatLunarYear(iLunarYear)
{
	var szText1 = "甲乙丙丁戊己庚辛壬癸";
	var szText2 = "子丑寅卯辰巳午未申酉戌亥";
	var strYear;
	strYear = szText1.substr((iLunarYear - 4) % 10, 1);
	strYear = strYear + szText2.substr((iLunarYear - 4) % 12, 1);
	return strYear + "年";
}

//将农历iLunarMonth月格式化成农历表示的字符串
function FormatLunarMonth(iLunarMonth)
{
	var szText = new String("正二三四五六七八九十");
	var strMonth;
	if (iLunarMonth <= 10)
	{
		strMonth = szText.substr(iLunarMonth - 1, 1);
	}
	else if (iLunarMonth == 11) strMonth = "十一";
	else strMonth = "十二";
	return strMonth + "月";
}

//将农历iLunarDay日格式化成农历表示的字符串
function FormatLunarDay(iLunarDay)
{
	var szText1 = new String("初十廿三");
	var szText2 = new String("一二三四五六七八九十");
	var strDay;
	if ((iLunarDay != 20) && (iLunarDay != 30))
	{
		strDay = szText1.substr((iLunarDay - 1) / 10, 1) + szText2.substr((iLunarDay - 1) % 10, 1);
	}
	else if (iLunarDay != 20)
	{
		strDay = szText1.substr(iLunarDay / 10, 1) + "十";
	}
	else
	{
		strDay = "二十";
	}
	return strDay;
}

//将公历日期转换为农历日期，返回农历表示的字符串
function GetLunarDateString(SolarDate)
{
	
	var tmp;
	var iLunarYear;
	var iLunarMonth;
	var iLunarDay;
	var Leap = false;
	var MinMilli = 1000 * 60;
	var HrMilli = MinMilli * 60;
	var DyMilli = HrMilli * 24;
	
	//从2001年1月1日算起，给定的公历日期已经过去的天数
	//11323是1970年1月1日到2001年1月1日之间的天数，因为Date是从1970年1月1日作为起点的
	var iSpanDays = Math.round(SolarDate.getTime() / DyMilli) - 11323;
	
	//公历2001年1月24日为农历2001年正月初一，差23天
	if (iSpanDays < 23)
	{
		iYear = 2000;
		iLunarMonth = 12;
		iLunarDay = iSpanDays + 7;
	}
	else
	{
		//从农历2001年正月初一算起
		iSpanDays = iSpanDays - 23;
		iLunarYear = 2001;
		iLunarMonth = 1;
		iLunarDay = 1;
		
		//计算农历年
		tmp = LunarYearDays(iLunarYear);
		while (iSpanDays >= tmp)
		{
			iSpanDays -= tmp;
			iLunarYear++;
			tmp = LunarYearDays(iLunarYear);
		}
		//计算农历月
		tmp = LunarMonthDays(iLunarYear, iLunarMonth) & 0xffff;//取低字
		while (iSpanDays >= tmp)
		{
			iSpanDays -= tmp;
			if (iLunarMonth == GetLeapMonth(iLunarYear))
			{
				//该年该月闰月
				tmp = LunarMonthDays(iLunarYear, iLunarMonth) >> 16;//取高字
				if (iSpanDays < tmp)
				{
					Leap = (tmp > 0) ? true : false;
					//闰月的后个月？
					break;
				}
				iSpanDays = iSpanDays - tmp;
			}
			iLunarMonth++;
			tmp = LunarMonthDays(iLunarYear,iLunarMonth) & 0xffff;//取低字
		}
		//计算农历日
		iLunarDay += iSpanDays;
	}
	return FormatLunarYear(iLunarYear) + (Leap ? "闰" : "") + FormatLunarMonth(iLunarMonth) + FormatLunarDay(iLunarDay);
}

//调用方法举例如下：
//var vDate = new Date(2006, 8, 28);
//document.write(GetLunarDateString(vDate));