JSFiddle - React, Tailwind, and code Playground

HTML

<div class="calendar">
    <div class="month">
        <div class="month-name">January</div>
    </div>
    <div class="day">
        <div class="day-number">21</div>
        <div class="day-name">Wednesday</div>
    </div>
</div>
<div class="button"></div>

CSS

body {
    padding: 20px;
    font-family: Arial;
}
.calendar {
    display: inline-block;
    width: 80px;
    height: 74px;
}
.calendar .month {
    background-color: firebrick;
    border-radius: 3px 3px 0 0;
}
.calendar .month-name {
    color: white;
    font-size: 13px;
    text-align: center;
    height: 26px;
}
.calendar .day {
    background-color: linen;
    border-radius: 0 0 3px 3px;
}
.calendar .day .day-number {
    color: black;
    font-size: 26px;
    font-weight: bold;
    text-align: center;
    height: 30px;
}
.calendar .day .day-name {
    color: darkgray;
    font-size: 10px;
    text-align: center;
    height: 18px;
}

.button {
    background-color: silver;
    display: inline-block;
    border-radius: 3px;
    width: 220px;
    height: 74px;
}