only show add link for today and future dates

app/views/common/_calendar.html.erb

@@ -65,10 +65,12 @@
             <span class="day-value"><%= day.day %></span>
             <span class="abbr-day">(<%= abbr_day_name(day.cwday) %>)</span>
             
+            <% if day >= User.current.today %>
               <%= link_to sprite_icon('add'),
                           new_customer_appointment_path(start_date: day),
                           class: 'icon-only icon-add',
                           title: l(:label_appointment_new, default: 'New Appointment') %>
+            <% end %>
           </p>
 
           <%