JSFiddle - React, Tailwind, and code Playground

HTML

<div class="calander">
    <div class="date">
        <div class="calandertext">&#60;</div>
    </div>
    <div class="month" id="month2">
        <div class="calandertext">April</div>
    </div>
    <div class="date">
        <div class="calandertext">&#62;</div>
    </div>
    <div class="row">
        <div class="day">
            <div class="calandertext">M</div>
        </div>
        <div class="day">
            <div class="calandertext">T</div>
        </div>
        <div class="day">
            <div class="calandertext">W</div>
        </div>
        <div class="day">
            <div class="calandertext">T</div>
        </div>
        <div class="day">
            <div class="calandertext">F</div>
        </div>
        <div class="day">
            <div class="calandertext">S</div>
        </div>
        <div class="day">
            <div class="calandertext">S</div>
        </div>
    </div>
    <div class="row">
        <div class="date">
            <div class="calandertext"></div>
        </div>
        <div class="date">
            <div class="calandertext">1</div>
        </div>
        <div class="date">
            <div class="calandertext">2</div>
        </div>
        <div class="date">
            <div class="calandertext">3</div>
        </div>
        <div class="date">
            <div class="calandertext">4</div>
        </div>
        <div class="date">
            <div class="calandertext">5</div>
        </div>
        <div class="date">
            <div class="calandertext">6</div>
        </div>
    </div>
    <div class="row">
        <div class="date">
            <div class="calandertext">7</div>
        </div>
        <div class="date">
            <div class="calandertext">8</div>
        </div>
        <div class="date">
            <div class="calandertext">9</div>
        </div>
        <div class="date">
            <div class="calandertext">10</div>
        </div>
        <div class="date">
            <div...

CSS

.calander {
    font-size: 0;
    width: 70%;
    height:400px;
    overflow-x:hidden;
    overflow-y:scroll;
}
.month {
    position: relative;
    height: 80px;
    background-color: #FFE06B;
    width: 71.4265%;
    display: inline-block;
}
.day.selected, .date.selected {
    border:2px solid #000;
    box-sizing:border-box;
}
.day {
    position: relative;
    height: 50px;
    background-color: #4DC3F0;
    display: inline-block;
    width: 14.2853%;
}
.date {
    position: relative;
    height: 80px;
    background-color: #FFE06B;
    display: inline-block;
    width: 14.2853%;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
}
.calandertext {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    top: 50%;
    text-align: center;
    line-height: 0;
    font-size: 40px;
}

JavaScript

var position = { x: 0, y: 0 };
var calendarMap = [];

$(document).ready(function () {
    $('.row').each(function () {
        calendarMap.push([]);
        $('.day, .date', this).each(function () {
            calendarMap[calendarMap.length - 1].push($(this));
        });
    });
    highlightCell();
});

$(window).on('keydown', function (e) {
    if (e.keyCode === 37) // left
        moveLeft();
    else if (e.keyCode === 38) // up
        moveUp();
    else if (e.keyCode === 39) // right
        moveRight();
    else if (e.keyCode === 40) // down
        moveDown();
    highlightCell();
});

function moveLeft() {
    position.x--;
    if (position.x < 0)
        position.x = 0;
}

function moveUp() {
    position.y--;
    if (position.y < 0)
        position.y = 0;
}

function moveRight() {
    position.x++;
    if (position.x >= calendarMap[0].length)
        position.x = calendarMap[0].length - 1;
}

function moveDown() {
    position.y++;
    if (position.y >= calendarMap.length)
        position.y = calendarMap.length - 1;
}

function highlightCell() {
    $('.day, .date').removeClass('selected');
    calendarMap[position.y][position.x].addClass('selected');
}