create.rb

class Create
  include Lotus::Action
  expose :booking, :errors
  
  def call(params)
    @booking = Booking.new
    
    # BookingForm validates datetime entered and converts the values into a single Time object
    form = BookingForm.new(booking)
    # Syncs the form values to the entity
    form.sync(params)
    
    # The contract validates that the booking is possible (no overlaps with other bookings)
    contract = BookingContract.new(booking)
    conract.validate
    
    @errors = Errors.new(form, contract)
    
    if errors.empty?
      BookingRepository.save(booking)
    else
      throw 422
    end
  end
end

new.html.erb

<form action="/bookings" method="post">
  <% errors.each do |error| %>
    <%= error %>
  <% end %>
  
  <label>When do you want to book a room?</label>
  <select name="booked_for[day]">...</select>
  <select name="booked_for[month]">...</select>
  <select name="booked_for[year]">...</select>
  <select name="booked_for[hour]">...</select>
  <select name="booked_for[minute]">...</select>
</form>