Activeadmin datepicker returning ISO formatted date but displaying in a custom date format

datepicker_input.rb

# Usage : f.input :my_date_field, as: :datepicker, datepicker_options: {dateFormat: 'mm-dd-yy'}
# Default dateFormat french : dd/mm/yy

class DatepickerInput < ActiveAdmin::Inputs::DatepickerInput
  def to_html
    input_wrapping do

      # New field options inherit from given input_html_options
      new_input_html_options = input_html_options
      # Avoid two inputs with the same id. Only the hidden input get the official id
      new_input_html_options[:id] = nil
      # Force text input
      new_input_html_options[:type] = "text"
      # Convert initial value to the specified jquery datepicker format
      value = @object.send(method)
      if value.is_a? Date
        new_input_html_options[:value] = value.strftime(convert_date_format_to_ruby(date_format))
      end
      # Empty input_html_options as the hidden field doesn't need it
      input_html_options = nil


      # Output label
      label_html <<
      # Output field as hidden field
      builder.hidden_field(method) <<
      # Output display date field
      template.content_tag(:input, "", new_input_html_options)
    end
  end

  private

    # Called in ActiveAdmin::Inputs::DatepickerInput#input_html_options
    def datepicker_options
      super.tap do |options|
        options[:datepicker_options]['dateFormat'] = date_format
        options[:datepicker_options]['altField'] = "##{dom_id}"
        options[:datepicker_options]['altFormat'] = 'yy-mm-dd'
      end

    end

    # Return the specified date_format or a default one
    def date_format
      if options[:datepicker_options].present? && options[:datepicker_options][:dateFormat].present?
        options[:datepicker_options][:dateFormat]
      else
        "dd/mm/yy"
      end
    end

    # Concert date format from jquery datepicker's one to ruby's one
    def convert_date_format_to_ruby(jquery_datepicker_format)
      jquery_datepicker_format.gsub(/dd|mm|yy|d|m|y/,
                                    'dd'=>'%d',
                                    'mm'=>'%m',
                                    'yy'=>'%Y',
                                    'd'=>'%-d',
                                    'm'=>'%-m',
                                    'y'=>'%y')
    end

end