diff --git a/jalali.js b/jalali.js
index 477bccb..c5827d8 100644
--- a/jalali.js
+++ b/jalali.js
@@ -5,6 +5,7 @@
  * See the GPL for details (http://www.gnu.org/licenses/gpl.html).
  * 
  * Based on code from http://farsiweb.info
+ * Edit: 2020=۱۳۹۹ (https://jdf.scr.ir/jdf/)
  */
 
 JalaliDate = {
@@ -12,110 +13,78 @@ JalaliDate = {
 	j_days_in_month: [31, 31, 31, 31, 31, 31, 30, 30, 30, 30, 30, 29]
 };
 
-JalaliDate.jalaliToGregorian = function(j_y, j_m, j_d)
-{
-	j_y = parseInt(j_y);
-	j_m = parseInt(j_m);
-	j_d = parseInt(j_d);
-	var jy = j_y-979;
-	var jm = j_m-1;
-	var jd = j_d-1;
-
-	var j_day_no = 365*jy + parseInt(jy / 33)*8 + parseInt((jy%33+3) / 4);
-	for (var i=0; i < jm; ++i) j_day_no += JalaliDate.j_days_in_month[i];
-
-	j_day_no += jd;
-
-	var g_day_no = j_day_no+79;
-
-	var gy = 1600 + 400 * parseInt(g_day_no / 146097); /* 146097 = 365*400 + 400/4 - 400/100 + 400/400 */
-	g_day_no = g_day_no % 146097;
-
-	var leap = true;
-	if (g_day_no >= 36525) /* 36525 = 365*100 + 100/4 */
-	{
-		g_day_no--;
-		gy += 100*parseInt(g_day_no/  36524); /* 36524 = 365*100 + 100/4 - 100/100 */
-		g_day_no = g_day_no % 36524;
-
-		if (g_day_no >= 365)
-			g_day_no++;
-		else
-			leap = false;
+JalaliDate.jalaliToGregorian = function (jy, jm, jd) {
+	[jy, jm, jd] = [parseInt(jy), parseInt(jm), parseInt(jd)];
+	var sal_a, gy, gm, gd, days;
+	jy += 1595;
+	days = -355668 + (365 * jy) + (parseInt(jy / 33) * 8) + parseInt(((jy % 33) + 3) / 4) + jd + ((jm < 7) ? (jm - 1) * 31 : ((jm - 7) * 30) + 186);
+	gy = 400 * parseInt(days / 146097);
+	days %= 146097;
+	if (days > 36524) {
+		gy += 100 * parseInt(--days / 36524);
+		days %= 36524;
+		if (days >= 365) days++;
 	}
-
-	gy += 4*parseInt(g_day_no/ 1461); /* 1461 = 365*4 + 4/4 */
-	g_day_no %= 1461;
-
-	if (g_day_no >= 366) {
-		leap = false;
-
-		g_day_no--;
-		gy += parseInt(g_day_no/ 365);
-		g_day_no = g_day_no % 365;
+	gy += 4 * parseInt(days / 1461);
+	days %= 1461;
+	if (days > 365) {
+		gy += parseInt((days - 1) / 365);
+		days = (days - 1) % 365;
 	}
-
-	for (var i = 0; g_day_no >= JalaliDate.g_days_in_month[i] + (i == 1 && leap); i++)
-		g_day_no -= JalaliDate.g_days_in_month[i] + (i == 1 && leap);
-	var gm = i+1;
-	var gd = g_day_no+1;
-
+	gd = days + 1;
+	sal_a = [0, 31, ((gy % 4 === 0 && gy % 100 !== 0) || (gy % 400 === 0)) ? 29 : 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
+	for (gm = 0; gm < 13 && gd > sal_a[gm]; gm++) gd -= sal_a[gm];
 	return [gy, gm, gd];
 }
 
-JalaliDate.checkDate = function(j_y, j_m, j_d)
-{
-	return !(j_y < 0 || j_y > 32767 || j_m < 1 || j_m > 12 || j_d < 1 || j_d >
-		(JalaliDate.j_days_in_month[j_m-1] + (j_m == 12 && !((j_y-979)%33%4))));
+JalaliDate.gregorianToJalali = function (gy, gm, gd) {
+	[gy, gm, gd] = [parseInt(gy), parseInt(gm), parseInt(gd)];
+	var g_d_m, jy, jm, jd, gy2, days;
+	g_d_m = [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334];
+	gy2 = (gm > 2) ? (gy + 1) : gy;
+	days = 355666 + (365 * gy) + parseInt((gy2 + 3) / 4) - parseInt((gy2 + 99) / 100) + parseInt((gy2 + 399) / 400) + gd + g_d_m[gm - 1];
+	jy = -1595 + (33 * parseInt(days / 12053));
+	days %= 12053;
+	jy += 4 * parseInt(days / 1461);
+	days %= 1461;
+	if (days > 365) {
+		jy += parseInt((days - 1) / 365);
+		days = (days - 1) % 365;
+	}
+	if (days < 186) {
+		jm = 1 + parseInt(days / 31);
+		jd = 1 + (days % 31);
+	} else {
+		jm = 7 + parseInt((days - 186) / 30);
+		jd = 1 + ((days - 186) % 30);
+	}
+	return [jy, jm, jd];
 }
 
-JalaliDate.gregorianToJalali = function(g_y, g_m, g_d)
-{
-	g_y = parseInt(g_y);
-	g_m = parseInt(g_m);
-	g_d = parseInt(g_d);
-	var gy = g_y-1600;
-	var gm = g_m-1;
-	var gd = g_d-1;
-
-	var g_day_no = 365*gy+parseInt((gy+3) / 4)-parseInt((gy+99)/100)+parseInt((gy+399)/400);
-
-	for (var i=0; i < gm; ++i)
-	g_day_no += JalaliDate.g_days_in_month[i];
-	if (gm>1 && ((gy%4==0 && gy%100!=0) || (gy%400==0)))
-	/* leap and after Feb */
-	++g_day_no;
-	g_day_no += gd;
-
-	var j_day_no = g_day_no-79;
-
-	var j_np = parseInt(j_day_no/ 12053);
-	j_day_no %= 12053;
-
-	var jy = 979+33*j_np+4*parseInt(j_day_no/1461);
-
-	j_day_no %= 1461;
-
-	if (j_day_no >= 366) {
-		jy += parseInt((j_day_no-1)/ 365);
-		j_day_no = (j_day_no-1)%365;
-	}
+JalaliDate.checkDate = function (py, pm, pd) {
+	return !(py < 0 || py > 32767 || pm < 1 || pm > 12 || pd < 1 || pd > JalaliDate.pDaysInMonth(py, pm));
+};
 
-	for (var i = 0; i < 11 && j_day_no >= JalaliDate.j_days_in_month[i]; ++i) {
-		j_day_no -= JalaliDate.j_days_in_month[i];
+JalaliDate.isKabiseh = function (py, outType = 'bool') {
+	types = {
+		'int': [0, 1],
+		'bool': [false, true],
+		'yearDays': [365, 366],
+		'esfandDays': [29, 30],
+		'farsi': ["کبیسه نیست", "کبیسه است"]
 	}
-	var jm = i+1;
-	var jd = j_day_no+1;
-
+	return ((((py % 33) % 4) - 1) === parseInt((py % 33) * 0.05)) ? types[outType][1] : types[outType][0];
+};
 
-	return [jy, jm, jd];
-}
+JalaliDate.pDaysInMonth = function (py, pm) {
+	return ((pm < 7) ? 31 : ((pm < 12) ? 30 : JalaliDate.isKabiseh(py, 'esfandDays')));
+};
 
-Date.prototype.setJalaliFullYear = function(y, m, d) {
+Date.prototype.setJalaliFullYear = function (y, m, d) {
 	var gd = this.getDate();
 	var gm = this.getMonth();
 	var gy = this.getFullYear();
-	var j = JalaliDate.gregorianToJalali(gy, gm+1, gd);
+	var j = JalaliDate.gregorianToJalali(gy, gm + 1, gd);
 	if (y < 100) y += 1300;
 	j[0] = y;
 	if (m != undefined) {
@@ -127,59 +96,59 @@ Date.prototype.setJalaliFullYear = function(y, m, d) {
 	}
 	if (d != undefined) j[2] = d;
 	var g = JalaliDate.jalaliToGregorian(j[0], j[1], j[2]);
-	return this.setFullYear(g[0], g[1]-1, g[2]);
+	return this.setFullYear(g[0], g[1] - 1, g[2]);
 }
 
-Date.prototype.setJalaliMonth = function(m, d) {
+Date.prototype.setJalaliMonth = function (m, d) {
 	var gd = this.getDate();
 	var gm = this.getMonth();
 	var gy = this.getFullYear();
-	var j = JalaliDate.gregorianToJalali(gy, gm+1, gd);
+	var j = JalaliDate.gregorianToJalali(gy, gm + 1, gd);
 	if (m > 11) {
 		j[0] += Math.floor(m / 12);
 		m = m % 12;
 	}
-	j[1] = m+1;
+	j[1] = m + 1;
 	if (d != undefined) j[2] = d;
 	var g = JalaliDate.jalaliToGregorian(j[0], j[1], j[2]);
-	return this.setFullYear(g[0], g[1]-1, g[2]);
+	return this.setFullYear(g[0], g[1] - 1, g[2]);
 }
 
-Date.prototype.setJalaliDate = function(d) {
+Date.prototype.setJalaliDate = function (d) {
 	var gd = this.getDate();
 	var gm = this.getMonth();
 	var gy = this.getFullYear();
-	var j = JalaliDate.gregorianToJalali(gy, gm+1, gd);
+	var j = JalaliDate.gregorianToJalali(gy, gm + 1, gd);
 	j[2] = d;
 	var g = JalaliDate.jalaliToGregorian(j[0], j[1], j[2]);
-	return this.setFullYear(g[0], g[1]-1, g[2]);
+	return this.setFullYear(g[0], g[1] - 1, g[2]);
 }
 
-Date.prototype.getJalaliFullYear = function() {
+Date.prototype.getJalaliFullYear = function () {
 	var gd = this.getDate();
 	var gm = this.getMonth();
 	var gy = this.getFullYear();
-	var j = JalaliDate.gregorianToJalali(gy, gm+1, gd);
+	var j = JalaliDate.gregorianToJalali(gy, gm + 1, gd);
 	return j[0];
 }
 
-Date.prototype.getJalaliMonth = function() {
+Date.prototype.getJalaliMonth = function () {
 	var gd = this.getDate();
 	var gm = this.getMonth();
 	var gy = this.getFullYear();
-	var j = JalaliDate.gregorianToJalali(gy, gm+1, gd);
-	return j[1]-1;
+	var j = JalaliDate.gregorianToJalali(gy, gm + 1, gd);
+	return j[1] - 1;
 }
 
-Date.prototype.getJalaliDate = function() {
+Date.prototype.getJalaliDate = function () {
 	var gd = this.getDate();
 	var gm = this.getMonth();
 	var gy = this.getFullYear();
-	var j = JalaliDate.gregorianToJalali(gy, gm+1, gd);
+	var j = JalaliDate.gregorianToJalali(gy, gm + 1, gd);
 	return j[2];
 }
 
-Date.prototype.getJalaliDay = function() {
+Date.prototype.getJalaliDay = function () {
 	var day = this.getDay();
 	day = (day + 1) % 7;
 	return day;
@@ -190,11 +159,11 @@ Date.prototype.getJalaliDay = function() {
  * Jalali UTC functions 
  */
 
-Date.prototype.setJalaliUTCFullYear = function(y, m, d) {
+Date.prototype.setJalaliUTCFullYear = function (y, m, d) {
 	var gd = this.getUTCDate();
 	var gm = this.getUTCMonth();
 	var gy = this.getUTCFullYear();
-	var j = JalaliDate.gregorianToJalali(gy, gm+1, gd);
+	var j = JalaliDate.gregorianToJalali(gy, gm + 1, gd);
 	if (y < 100) y += 1300;
 	j[0] = y;
 	if (m != undefined) {
@@ -206,59 +175,59 @@ Date.prototype.setJalaliUTCFullYear = function(y, m, d) {
 	}
 	if (d != undefined) j[2] = d;
 	var g = JalaliDate.jalaliToGregorian(j[0], j[1], j[2]);
-	return this.setUTCFullYear(g[0], g[1]-1, g[2]);
+	return this.setUTCFullYear(g[0], g[1] - 1, g[2]);
 }
 
-Date.prototype.setJalaliUTCMonth = function(m, d) {
+Date.prototype.setJalaliUTCMonth = function (m, d) {
 	var gd = this.getUTCDate();
 	var gm = this.getUTCMonth();
 	var gy = this.getUTCFullYear();
-	var j = JalaliDate.gregorianToJalali(gy, gm+1, gd);
+	var j = JalaliDate.gregorianToJalali(gy, gm + 1, gd);
 	if (m > 11) {
 		j[0] += Math.floor(m / 12);
 		m = m % 12;
 	}
-	j[1] = m+1;
+	j[1] = m + 1;
 	if (d != undefined) j[2] = d;
 	var g = JalaliDate.jalaliToGregorian(j[0], j[1], j[2]);
-	return this.setUTCFullYear(g[0], g[1]-1, g[2]);
+	return this.setUTCFullYear(g[0], g[1] - 1, g[2]);
 }
 
-Date.prototype.setJalaliUTCDate = function(d) {
+Date.prototype.setJalaliUTCDate = function (d) {
 	var gd = this.getUTCDate();
 	var gm = this.getUTCMonth();
 	var gy = this.getUTCFullYear();
-	var j = JalaliDate.gregorianToJalali(gy, gm+1, gd);
+	var j = JalaliDate.gregorianToJalali(gy, gm + 1, gd);
 	j[2] = d;
 	var g = JalaliDate.jalaliToGregorian(j[0], j[1], j[2]);
-	return this.setUTCFullYear(g[0], g[1]-1, g[2]);
+	return this.setUTCFullYear(g[0], g[1] - 1, g[2]);
 }
 
-Date.prototype.getJalaliUTCFullYear = function() {
+Date.prototype.getJalaliUTCFullYear = function () {
 	var gd = this.getUTCDate();
 	var gm = this.getUTCMonth();
 	var gy = this.getUTCFullYear();
-	var j = JalaliDate.gregorianToJalali(gy, gm+1, gd);
+	var j = JalaliDate.gregorianToJalali(gy, gm + 1, gd);
 	return j[0];
 }
 
-Date.prototype.getJalaliUTCMonth = function() {
+Date.prototype.getJalaliUTCMonth = function () {
 	var gd = this.getUTCDate();
 	var gm = this.getUTCMonth();
 	var gy = this.getUTCFullYear();
-	var j = JalaliDate.gregorianToJalali(gy, gm+1, gd);
-	return j[1]-1;
+	var j = JalaliDate.gregorianToJalali(gy, gm + 1, gd);
+	return j[1] - 1;
 }
 
-Date.prototype.getJalaliUTCDate = function() {
+Date.prototype.getJalaliUTCDate = function () {
 	var gd = this.getUTCDate();
 	var gm = this.getUTCMonth();
 	var gy = this.getUTCFullYear();
-	var j = JalaliDate.gregorianToJalali(gy, gm+1, gd);
+	var j = JalaliDate.gregorianToJalali(gy, gm + 1, gd);
 	return j[2];
 }
 
-Date.prototype.getJalaliUTCDay = function() {
+Date.prototype.getJalaliUTCDay = function () {
 	var day = this.getUTCDay();
 	day = (day + 1) % 7;
 	return day;