Have you tried:
http://jsfiddle.net/sanpopo/byRTn/
table.calendar {
table-layout: fixed;
width: 520px;
}
span.day-number {
vertical-align:top;
background:#999;
z-index:2;
top:0px;
padding:4px;
color:#fff;
font-weight:bold;
width:18px;
text-align:center;
float:right;
}
td.calendar-day, td.calendar-day-np {
// float:left;
vertical-align:top;
width:70px;
border-bottom:1px solid #999;
border-right:1px solid #999;
}
div.event {
display:inline;
position:relative;
z-index:3;
top:30px;
text-width: 70px;
}