* {
    box-sizing: border-box;
}    

body {
    margin: 0;
    background: no-repeat center center fixed; 
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
    color: white;
    font-family: Arial, Helvetica, sans-serif;
    text-shadow: 0px 0px 20px #aaaaaa;
}

main {
    padding: 15px;
    height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}

div.top {
    display: flex;
    justify-content: space-between;
}

h1.time {
    text-align: center;
}