function mod(a, b)
{
    return a - (b * Math.floor(a / b));
}
function jwday(j)
{
    return mod(Math.floor((j + 1.5)), 7);
}
var Weekdays = new Array( "Sunday", "Monday", 
                          "Tuesday", "Wednesday",
                          "Thursday", "Friday", "Saturday" );
//  LEAP_GREGORIAN  --  Is a given year in the Gregorian calendar a leap year ?
function leap_gregorian(year)
{
    return ((year % 4) == 0) &&
            (!(((year % 100) == 0) && ((year % 400) != 0)));
}
//  GREGORIAN_TO_JD  --  Determine Julian day number from Gregorian calendar date
var GREGORIAN_EPOCH = 1721425.5;
function gregorian_to_jd(year, month, day)
{
    return (GREGORIAN_EPOCH - 1) +
           (365 * (year - 1)) +
           Math.floor((year - 1) / 4) +
           (-Math.floor((year - 1) / 100)) +
           Math.floor((year - 1) / 400) +
           Math.floor((((367 * month) - 362) / 12) +
           ((month <= 2) ? 0 :
                               (leap_gregorian(year) ? -1 : -2)
           ) +
           day);
}
//  JD_TO_GREGORIAN  --  Calculate Gregorian calendar date from Julian day
function jd_to_gregorian(jd) {
    var wjd, depoch, quadricent, dqc, cent, dcent, quad, dquad,
        yindex, dyindex, year, yearday, leapadj;
    wjd = Math.floor(jd - 0.5) + 0.5;
    depoch = wjd - GREGORIAN_EPOCH;
    quadricent = Math.floor(depoch / 146097);
    dqc = mod(depoch, 146097);
    cent = Math.floor(dqc / 36524);
    dcent = mod(dqc, 36524);
    quad = Math.floor(dcent / 1461);
    dquad = mod(dcent, 1461);
    yindex = Math.floor(dquad / 365);
    year = (quadricent * 400) + (cent * 100) + (quad * 4) + yindex;
    if (!((cent == 4) || (yindex == 4))) {
        year++;
    }
    yearday = wjd - gregorian_to_jd(year, 1, 1);
    leapadj = ((wjd < gregorian_to_jd(year, 3, 1)) ? 0
                                                  :
                  (leap_gregorian(year) ? 1 : 2)
              );
    month = Math.floor((((yearday + leapadj) * 12) + 373) / 367);
    day = (wjd - gregorian_to_jd(year, month, 1)) + 1;
    return new Array(year, month, day);
}
//  LEAP_PERSIAN  --  Is a given year a leap year in the Persian calendar ?
function leap_persian(year)
{
    return ((((((year - ((year > 0) ? 474 : 473)) % 2820) + 
                          474) + 38) * 682) % 2816) < 682;
}
//  PERSIAN_TO_JD  --  Determine Julian day from Persian date
var PERSIAN_EPOCH = 1948320.5;
var PERSIAN_WEEKDAYS = new Array(
    "شنبه", "یکشنبه","دوشنبه", 
    "سه شنبه","چهارشنبه", "پنج شنبه", "جمعه");
function persian_to_jd(year, month, day)
{
    var epbase, epyear;
    epbase = year - ((year >= 0) ? 474 : 473);
    epyear = 474 + mod(epbase, 2820);
    return day +
            ((month <= 7) ?
                ((month - 1) * 31) :
                (((month - 1) * 30) + 6)
            ) +
            Math.floor(((epyear * 682) - 110) / 2816) +
            (epyear - 1) * 365 +
            Math.floor(epbase / 2820) * 1029983 +
            (PERSIAN_EPOCH - 1);
}
//  JD_TO_PERSIAN  --  Calculate Persian date from Julian day
function jd_to_persian(jd)
{
    var year, month, day, depoch, cycle, cyear, ycycle,
        aux1, aux2, yday;
    jd = Math.floor(jd) + 0.5;
    depoch = jd - persian_to_jd(475, 1, 1);
    cycle = Math.floor(depoch / 1029983);
    cyear = mod(depoch, 1029983);
    if (cyear == 1029982) {
        ycycle = 2820;
    } else {
        aux1 = Math.floor(cyear / 366);
        aux2 = mod(cyear, 366);
        ycycle = Math.floor(((2134 * aux1) + (2816 * aux2) + 2815) / 1028522) +
                    aux1 + 1;
    }
    year = ycycle + (2820 * cycle) + 474;
    if (year <= 0) {
        year--;
    }
    yday = (jd - persian_to_jd(year, 1, 1)) + 1;
    month = (yday <= 186) ? Math.ceil(yday / 31) : Math.ceil((yday - 6) / 30);
    day = (jd - persian_to_jd(year, month, 1)) + 1;
    return new Array(year, month, day);
}
function calcPersian(year,month,day)
{
    var date,j;

    j = persian_to_jd(year,month,day);
    date = jd_to_gregorian(j);
    weekday = jwday(j);
    return new Array(date[0], date[1], date[2],weekday);
}
//  calcGregorian  --  Perform calculation starting with a Gregorian date
function calcGregorian(year,month,day)
{
    month--;
    var j, weekday;
    //  
    j = gregorian_to_jd(year, month + 1, day) +
           (Math.floor(0 + 60 * (0 + 60 * 0) + 0.5) / 86400.0);
    //  
    perscal = jd_to_persian(j);
    weekday = jwday(j);
    return new Array(perscal[0], perscal[1], perscal[2],weekday);
}
function getTodayGregorian()
{
    var t = new Date();
    var today = new Date();
    var y = today.getYear();
    if (y < 1000) {
        y += 1900;
    }
    return new Array(y, today.getMonth() + 1, today.getDate(),t.getDay());
}
function getTodayPersian()
{
    var t = new Date();
    var today = getTodayGregorian();

    var persian = calcGregorian(today[0],today[1],today[2]);
    return new Array(persian[0],persian[1],persian[2]);
}