Let's go through the code above from top to bottom.

Instantiate a BookableCell plugin object.
Instantiate a Calendar object.
Hook the BookableCell object into Calendar object.
Call the BookableCell object's routing function.
Render the calendar.
Last missing puzzle is the css file, create a file calendar.css, copy and paste the code below:
/*******************************Calendar Top Navigation*********************************/
body {
    font-family: "Arial";
}
 
 .weekend {
    background-color: red;
}

div#calendar {
    margin: 0px auto;
    padding: 0px;
    width: 602px;
}
 
div#calendar div.box {
    position: relative;
    top: 0px;
    left: 0px;
    width: 100%;
    height: 40px;
    background-color: #3FA7D6;
}
 
div#calendar div.header {
    line-height: 40px;
    vertical-align: middle;
    position: absolute;
    left: 11px;
    top: 0px;
    width: 582px;
    height: 40px;
    text-align: center;
}
 
div#calendar div.header a.prev, div#calendar div.header a.next {
    position: absolute;
    top: 0px;
    height: 17px;
    display: block;
    cursor: pointer;
    text-decoration: none;
    color: #FFF;
}
 
div#calendar div.header span.title {
    color: #FFF;
    font-size: 18px;
}
 
div#calendar div.header a.prev {
    left: 0px;
}
 
div#calendar div.header a.next {
    right: 0px;
}
 
/*******************************Calendar Content Cells*********************************/
div#calendar div.box-content {
    border: 1px solid #3FA7D6;
    border-top: none;
}
 
div#calendar ul.label {
    float: left;
    margin: 0px;
    padding: 0px;
    margin-top: 5px;
    margin-left: 5px;
}
 
div#calendar ul.label li {
    margin: 0px;
    padding: 0px;
    margin-right: 5px;
    float: left;
    list-style-type: none;
    width: 80px;
    height: 40px;
    line-height: 40px;
    vertical-align: middle;
    text-align: center;
    color: #000;
    font-size: 15px;
    background-color: transparent;
}
 
div#calendar ul.dates {
    float: left;
    margin: 0px;
    padding: 0px;
    margin-left: 5px;
    margin-bottom: 5px;
}
 
/** overall width = width+padding-right**/
div#calendar ul.dates li {
    margin: 0px;
    padding: 0px;
    margin-right: 5px;
    margin-top: 5px;
    line-height: 80px;
    vertical-align: middle;
    float: left;
    list-style-type: none;
    width: 80px;
    height: 80px;
    font-size: 25px;
    background-color: #FFF;
    color: #000;
    text-align: center;
    position: relative;
}
 
:focus {
    outline: none;
}
 
div.clear {
    clear: both;
}
 
li div {
    display: flex;
}
 
li div form {
    display: inline;
    align-self: center;
    margin: 0;
    position: absolute;
    bottom: 2px;
}
 
div.open {
    background: #59CD90;
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    flex-direction: column;
    text-align: center;
}
 
div.booked {
    background: #D36135;
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    flex-direction: column;
    text-align: center;
    line-height: inherit;
}
 
.submit {
    box-shadow:inset 0px 1px 0px 0px #ffffff;
    background:linear-gradient(to bottom, #ffffff 5%, #f6f6f6 100%);
    background-color:#ffffff;
    border-radius:3px;
    border:1px solid #dcdcdc;
    display:inline-block;
    cursor:pointer;
    color:#666666;
    font-size:10px;
    font-weight:bold;
    padding:3px 12px;
    text-decoration:none;
    text-shadow:0px 1px 0px #ffffff;
}
 
.submit:hover {
    background:linear-gradient(to bottom, #f6f6f6 5%, #ffffff 100%);
    background-color:#f6f6f6;
}
.submit:active {
    position:relative;
    top:1px;
}