Making a solar calendar. Hijri Shamsi (Persian, solar) to Gregorian calendar

[Juan_Antonio]

Here the code...

<script>
     var PERSIAN_EPOCH = 1948320.5;

    datos =  window.AppInventor.getWebViewString(); // Entrada de datos App Inventor
  
    partes = datos.split(","); 
	var years = partes[0];
	var months = partes[1];
    var days = partes[2];
	
/*  MOD  --  Modulus function which works for non-integers.  (from file calendar.js original) */

function mod(a, b)
{
    return a - (b * Math.floor(a / b));
}
	
// PERSIAN_TO_JD -- Start data here

function persian_to_jd(year, month, day)
{
    var epbase, epyear;

    epbase = year - ((year >= 0) ? 474 : 473);
    epyear = 474 + mod(epbase, 2820);
    var salida = Number(day) +  Number(((month <= 7) ? ((month - 1) * 31) : (((month - 1) * 30) + 6)))  +
            Number(Math.floor(((epyear * 682) - 110) / 2816))  +  
			Number((epyear - 1) * 365) +
			Number(Math.floor(epbase / 2820) * 1029983) +  
			Number(PERSIAN_EPOCH -1);
  //  window.AppInventor.setWebViewString(salida);  // Juliano. Respuesta a CadenaDeWebView
   return salida
}
 
//  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;

	// Salida de calendario Gregoriano.
	 window.AppInventor.setWebViewString(year + "," + month + "," + day);  // Respuesta a CadenaDeWebView
    return new Array(year, month, day);
}

var juliano =  persian_to_jd(years,months,days);
var gregoriano = jd_to_gregorian(juliano);
</script>

Look at the Persian, Julian and Gregorian conversion algorithm.
As well as App Inventor data input and output.

calendario_persa.aia (3.6 KB)