private boolean isEqual(Object instance){
	    if (instance instanceof DateTime){
	    	DateTime dateTime = (DateTime)instance;
	    	if ((dateTime.getYear() == this.getYear()) 
	    			&& (dateTime.getMonth() == (this.getMonth()) 
	    			&& (dateTime.getDay() == this.getDay()))
	    			&& (dateTime.getHour() == this.getHour())
	    			&& (dateTime.getMinute() == this.getMinute())
	    			&& (dateTime.getSecond() == this.getSecond())){
	    		return true;
	    	}
	    	else{
	    		return false;
	    	}
	    }
	    else{
	    	return false;
	    }
	}