body {
    font-family: Arial, sans-serif;
    text-align: center;
    background-color: #121212;
    color: #ffffff;
}
#calendar {
    max-width: 400px;
    margin: auto;
    padding: 10px;
    border: 1px solid #444;
    border-radius: 10px;
    background-color: #1e1e1e;
}
.day {
    padding: 10px;
    border: 1px solid #555;
    border-radius: 5px;
    cursor: pointer;
    background-color: #2e2e2e;
    color: #ffffff;
}
.holiday {
    background-color: red;
    color: white;
}