anchor.diff:      height = g_height + header_height - 1
       wday = @gantt.date_from.cwday
     %>
  -  <% (@gantt.date_to - @gantt.date_from + 1).to_i.times do %>
  +  <% (@gantt.date_from).upto(@gantt.date_to) do |day| %>
       <%
         width =  zoom - 1
         style  = ""
  
positive.code:     %>
      <%= content_tag(:div, :style => style, :class => clss) do %>
        <%= day_letter(wday) %>
      <% end %>
      <%
        left = left + width + 1
  
negative.code:   headers_height = header_height
    show_weeks = false
    show_days  = false
    show_day_numbers = 
  
    if @gantt.zoom > 1
      show_weeks = true
  