JSFiddle - React, Tailwind, and code Playground

HTML

<button id="botao">Clique</button>
<div id="resultado">
    <p>Day-0</p>
</div>

CSS

body, div, p, button {
    font-family: tahoma, arial, sans-serif;
    font-size: 12px;
}
#resultado {
    background: #EEEEEE;
    margin: 0px;
    padding: 0px;
}
p {
    margin: 10px 0;
    padding: 10px;
    color: #666666;
}
button {
    background: #5588BB;
    color: #FFFFFF;
    border: 0;
    text-transform: uppercase;
    padding: 8px 12px;
    -webkit-border-radius: 3px;
    -moz-border-radius: 3px;
    border-radius: 3px;
}
button:hover {
    outline: 0;
    background-color: #6699CC;
}
button:focus {
    background: #77DDAA;
    outline: 0;
}

JavaScript

var valor = 0;
$('#botao').on('click', function () {
    valor++;
    $(this).data('order', 'Day-' + valor);
    $('#resultado p').html( $(this).data('order') );
});