Tony's ES6

class Day {
    constructor(month, day, year){
        this.month = month;
        this.day = day;
        this.year = year;
    }
}

class Tomorrow extends Day {
    constructor(month, day, year){
        super(month, day, year);
        this.activities = [];
        this.finalPlan;
    }
    addToDo(activity){
        this.activities.push(activity);
    }
    removeToDo(activity){
        var removing = this.activities.find(el=> el === activity);
        if(!removing) this.activities.splice(removing, 1);
    }
    getFinalPlan(){
        function finalize(activities){
            return activities.reduce(prev, curr, idx => {
                return prev + idx + '. ' + curr + '. \n';
            }, '');
        }
        if(!this.finalPlan) this.finalPlan = finalize(this.activities);
        return this.finalPlan;

    }
    readFinalPlan(){
        if(this.finalPlan) console.log(this.finalPlan);
        else console.log('Tomorrow\'s plans have not been finalized.');
    }
}

var juneThirteenthTwoThousandFifteen = new Tomorrow(6, 13, 2015);
juneThirteenthTwoThousandFifteen.addToDo('pushcart study room');
juneThirteenthTwoThousandFifteen.addToDo('more stuff');