function toGregorian(oPersian) {
		var iJulianDayNumber = j2d(oPersian.year, oPersian.month + 1, oPersian.day);
		return d2g(iJulianDayNumber);
	}
Calculate gregorian date from Persian

@param {object} oPersian a JS object containing day, month and year in the Persian calendar
@private