```ruby
require "gds_api/calendars"

class WorkingDaysCalculator
  def initialize(starting_from, in_division: :england_and_wales)
    @starting_from = starting_from
    @calendar_division = in_division
  end

  def after(how_many_days, skip_days: 0)
    days = (@starting_from.tomorrow..(@starting_from + how_many_days + skip_days))
    calculated_skip_days = days.count { |day| holiday?(day) }
    return days.last if calculated_skip_days == skip_days

    after(how_many_days, skip_days: calculated_skip_days)
  end

  def holiday?(date)
    date.saturday? || date.sunday? || public_holidays.include?(date)
  end

  def public_holidays
    @public_holidays ||= fetch_public_holidays
  end

private

  def fetch_public_holidays
    public_holidays_json = calendars_api.bank_holidays(@calendar_division)
    public_holidays_json["events"].map { |event| Date.parse(event["date"]) }
  end

  def calendars_api
    endpoint = if !Rails.env.production? || ENV["HEROKU_APP_NAME"].present?
                 Plek.new.website_root
               else
                 Plek.find("frontend")
               end
    GdsApi::Calendars.new(endpoint)
  end
end
```

Revert "Use internal Frontend API"
user
```ruby
require "gds_api/calendars"

class WorkingDaysCalculator
  def initialize(starting_from, in_division: :england_and_wales)
    @starting_from = starting_from
    @calendar_division = in_division
  end

  def after(how_many_days, skip_days: 0)
    days = (@starting_from.tomorrow..(@starting_from + how_many_days + skip_days))
    calculated_skip_days = days.count { |day| holiday?(day) }
    return days.last if calculated_skip_days == skip_days

    after(how_many_days, skip_days: calculated_skip_days)
  end

  def holiday?(date)
    date.saturday? || date.sunday? || public_holidays.include?(date)
  end

  def public_holidays
    @public_holidays ||= fetch_public_holidays
  end

private

  def fetch_public_holidays
    public_holidays_json = GdsApi.calendars.bank_holidays(@calendar_division)
    public_holidays_json["events"].map { |event| Date.parse(event["date"]) }
  end
end
```
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