Site.renderLinkToPrevMonth (firstDayIndex, currentMonth, monthNames)
check if there are any stories in the previous month

Sourcecode in Site/renderFunctions.js:
1:   function renderLinkToPrevMonth(firstDayIndex, currentMonth, monthNames) {
2:      var l = this.size();
3:      if (l == 0 || l <= firstDayIndex)
4:         return "&nbsp;";
5:   
6:      var prevDay = this.get(firstDayIndex + 1);
7:      if (prevDay && prevDay.groupname < currentMonth) {
8:         var month = prevDay.groupName.toString().substring(4, 6) - 1;
9:         return Html.linkAsString({href: prevDay.href()}, monthNames[month]);
10:     } else {
11:        return "&nbsp;";
12:     }
13:  }