html,
body {
    padding: 0;
    height: 100%;
    width: 100%;
}

#timedisplay {
    position: fixed;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;

    width: 100%;
    height: 210px;

    text-align: center;

    margin: auto;
}