tfaker/methods/islamicDate.js

Lightweight, Targaryen-themed lil' brother of faker.js

var gmod = function(n, m) {
  return ((n % m) + m) % m;
};

function kuwaiticalendar(adjust) {
  var myRes = new Array(8);
  var today = new Date();
  var day = today.getDate();
  var month = today.getMonth();
  var year = today.getFullYear();
  var m = month + 1;
  var y = year;
  var a = Math.floor(y / 100);
  var b = 2 - a + Math.floor(a / 4);

  var jd =
    Math.floor(365.25 * (y + 4716)) +
    Math.floor(30.6001 * (m + 1)) +
    day +
    b -
    1524;
  if (adjust && typeof adjust === "number") {
    myRes[0] = day; //calculated day (CE)
    myRes[1] = month - 1; //calculated month (CE)
    myRes[2] = year; //calculated year (CE)
    myRes[3] = jd - 1; //ju
    var adjustmili = 1000 * 60 * 60 * 24 * adjust;
    var todaymili = today.getTime() + adjustmili;
    today = new Date(todaymili);
  }


  if (m < 3) {
    y -= 1;
    m += 12;
  }

  if (y < 1583) {
    b = 0;
  }
  if (y === 1582) {
    if (m > 10) {
      b = -10;
    }
    if (m === 10) {
      b = 0;
      if (day > 4) {
        b = -10;
      }
    }
  }

  b = 0;
  if (jd > 2299160) {
    a = Math.floor((jd - 1867216.25) / 36524.25);
    b = 1 + a - Math.floor(a / 4);
  }
  var bb = jd + b + 1524;
  var cc = Math.floor((bb - 122.1) / 365.25);
  var dd = Math.floor(365.25 * cc);
  var ee = Math.floor((bb - dd) / 30.6001);
  day = bb - dd - Math.floor(30.6001 * ee);
  month = ee - 1;
  if (ee > 13) {
    cc += 1;
    month = ee - 13;
  }
  year = cc - 4716;

  var wd;
  if (adjust) {
    wd = gmod(jd + 1 - adjust, 7) + 1;
  } else {
    wd = gmod(jd + 1, 7) + 1;
  }

  var iyear = 10631 / 30;
  var epochastro = 1948084;
  //  var epochcivil = 1948085;   <--- EPOCHCIVIL unused var, if uncomment goto 68

  var shift1 = 8.01 / 60;

  var z = jd - epochastro;
  var cyc = Math.floor(z / 10631);
  z = z - 10631 * cyc;
  var j = Math.floor((z - shift1) / iyear);
  var iy = 30 * cyc + j;
  z = z - Math.floor(j * iyear + shift1);
  var im = Math.floor((z + 28.5001) / 29.5);
  if (im === 13) {
    im = 12;
  }
  var id = z - Math.floor(29.5001 * im - 29);

  myRes[0] = day; //calculated day (CE)
  myRes[1] = month - 1; //calculated month (CE)
  myRes[2] = year; //calculated year (CE)
  myRes[3] = jd - 1; //julian day number
  myRes[4] = wd - 1; //weekday number
  myRes[5] = id; //islamic date
  myRes[6] = im - 1; //islamic month
  myRes[7] = iy; //islamic year
  return myRes;
}

module.exports = function islamicDate(adjustment) {
  var wdNames = new Array(
    "Ahad",
    "Ithnin",
    "Thulatha",
    "Arbaa",
    "Khams",
    "Jumuah",
    "Sabt"
  );
  var iMonthNames = new Array(
    "Muharram",
    "Safar",
    "Rabi'ul Awwal",
    "Rabi'ul Akhir",
    "Jumadal Ula",
    "Jumadal Akhira",
    "Rajab",
    "Sha'ban",
    "Ramadan",
    "Shawwal",
    "Dhul Qa'ada",
    "Dhul Hijja"
  );

  if (adjustment === "zif" || adjustment === "fake") {
    var randomPast = kuwaiticalendar(
      -Math.round(Math.random() * 90 * 365.2422)
    );
    var fakeIDate =
      wdNames[Math.round(Math.random() * 7)] +
      ", " +
      randomPast[5] +
      " " +
      iMonthNames[randomPast[6]] +
      " " +
      randomPast[7] +
      " AH";
    return fakeIDate;
  } else {
    var iDate = kuwaiticalendar(adjustment);
    var outputIslamicDate =
      wdNames[iDate[4]] +
      ", " +
      iDate[5] +
      " " +
      iMonthNames[iDate[6]] +
      " " +
      iDate[7] +
      " AH";
    return outputIslamicDate;
  }
};

// original source : https://www.al-habib.info/islamic-calendar/hijricalendartext.htm