Group where no appointment

The code below shows number of appointment each hour and 'No appointment' if no appointment is available.

I want to group consecutive 'No appointment' slot according to time

for e.g., The output of the current code is -

10:00 AM to 11:00 AM -> No Appointment 11:00 AM to 12:00 PM -> No Appointment 12:00 PM to 01:00 PM -> No Appointment

I want the output to be

10:00 AM to 01:00 PM -> No Appointment

The code is give below:-

<% @time_group = ['6:00:00','7:00:00','8:00:00','9:00:00','10:00:00','11:00:00','12:00:00','13:00:00','14:00:00','15:00:00','16:00:00','17:00:00','18:00:00','19:00:00','20:00:00','21:00:00','22:00:00','23:00:00'] %>

#Loop through each hour in @time_group
<% @time_group.each_with_index do |t,index| %>
  <% t1 = Time.parse(t) %>
  <% t2 = Time.parse(t) + 3600 %>
  <% @booked = Appointment.where(start_time: t1..t2 %>

  #Show time interval e.g 1:00 PM to 2:00 PM
  <%= Time.parse(t).strftime('%I:%M %p') %> to <%= (Time.parse(t) + 3600).strftime('%I:%M %p') %>

   #if appointment is available show appointment else show no appointment
  <% if @booked.size > 0 %>

    <% @booked.each do |app| %>
      <%= app.start_time.strftime('%I:%M') %>  
    <% end %>

  <% else %>  

    No Appointment

  <% end %>
<% end %>