body{
    font-family:Arial;
    background:#f4f4f4;
    text-align:center;
}

.contenedor{
    margin-top:20px;
}

.reloj{
    margin:auto;
    width:400px;
}

button{

    width:250px;
    padding:15px;
    margin:10px;
    font-size:18px;
    cursor:pointer;
}