// 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, // 2001-2010
    0xb4a0, 0xb550, 0xb550, 0x55a8, 0x4ba0, 0xa5b0, 0x52b8, 0x52b0, 0xa930, 0x74a8, // 2011-2020
    0x6aa0, 0xad50, 0x4da8, 0x4b60, 0x9570, 0xa4e0, 0xd260, 0xe930, 0xd530, 0x5aa0, // 2021-2030
    0x6b50, 0x96d0, 0x4ae8, 0x4ad0, 0xa4d0, 0xd258, 0xd250, 0xd520, 0xdaa0, 0xb5a0, // 2031-2040
    0x56d0, 0x4ad8, 0x49b0, 0xa4b8, 0xa4b0, 0xaa50, 0xb528, 0x6d20, 0xada0, 0x55b0  // 2041-2050
);

// 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, // 2001-2010
    0x04, 0x09, 0x00, 0x60, 0x04, // 2011-2020
    0x00, 0x20, 0x60, 0x05, 0x00, // 2021-2030
    0x30, 0xb0, 0x06, 0x00, 0x50, // 2031-2040
    0x02, 0x07, 0x00, 0x50, 0x03  // 2041-2050
);


// 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 = new String("甲乙丙丁戊己庚辛壬癸");
    var szText2 = new String("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);
}
<!--
var today = new Date();
var seconds = today.getSeconds();
var enabled = 0;   today = new Date();
var day;
var date1;
var date2;
var date3;
var sx;
if(today.getDay()==0)     day = "星期日"
if(today.getDay()==1)     day = "星期一"
if(today.getDay()==2)     day = "星期二"
if(today.getDay()==3)     day = "星期三"
if(today.getDay()==4)     day = "星期四"
if(today.getDay()==5)     day = "星期五"
if(today.getDay()==6)     day = "星期六"




<!-- Begin
function signs() {
var start = 1901, birthyear = today.getYear();

x = (start - birthyear) % 12
if (x == 1 || x == -11) {value = "鼠";}
if (x == 0) {value = "牛";}
if (x == 11 || x == -1) {value = "虎";}
if (x == 10 || x == -2) {value = "兔";}
if (x == 9 || x == -3)  {value = "龙";}
if (x == 8 || x == -4)  {value ="蛇";}
if (x == 7 || x == -5)  {value = "马";}
if (x == 6 || x == -6)  {value = "羊";}
if (x == 5 || x == -7)  {value = "猴";}
if (x == 4 || x == -8)  {value = "鸡";}
if (x == 3 || x == -9)  {value = "狗";}
if (x == 2 || x == -10)  {value = "猪";}
return value;

}
sx="["+signs()+"]";

//  End -->



date1 =today.getYear()+ " 年 " + (today.getMonth() + 1 ) + " 月 " +
today.getDate() + " 日 " + " " + "("+day+")"+" &nbsp;";

date2 = GetLunarDateString(today);

date3=sx+" "+"农历"+date2;

document.write(date3);

