openproject/app/views/common/_calendar.rhtml

<table class="cal">
<thead>
<tr><td></td><% 7.times do |i| %><th><%= day_name( (calendar.first_wday+i)%7 ) %></th><% end %></tr>
</thead>
<tbody>
<tr>
<% day = calendar.startdt
while day <= calendar.enddt %>
<%= "<th>#{day.cweek}</th>" if day.cwday == calendar.first_wday %>
<td class="<%= day.month==calendar.month ? 'even' : 'odd' %><%= ' today' if Date.today == day %>">
<p class="day-num"><%= day.day %></p>	
<% calendar.events_on(day).each do |i| %>
  <% if i.is_a? Issue %>
  <div class="tooltip">
  <%= if day == i.start_date && day == i.due_date
        image_tag('arrow_bw.png')
      elsif day == i.start_date
        image_tag('arrow_from.png') 
      elsif day == i.due_date
		image_tag('arrow_to.png') 
      end %>
  <%= h("#{i.project} -") unless @project && @project == i.project %>
  <%= link_to_issue i %>: <%= h(truncate(i.subject, :length => 30)) %>
  <span class="tip"><%= render_issue_tooltip i %></span>
  </div>
  <% else %>
  <span class="icon icon-package">  
    <%= h("#{i.project} -") unless @project && @project == i.project %>
    <%= link_to_version i%>
  </span>
  <% end %>
<% end %>
</td>
<%= '</tr><tr>' if day.cwday==calendar.last_wday and day!=calendar.enddt %>
<% day = day + 1
end %>
</tr>
</tbody>
</table>