How to fake Date.current?

gistfile1.rb

  def adjusted real_value, type, &block
    puts @data
    key = [real_value, type]
    if @data.include? key
      @data[key][1]= Date.current   # <- calls  Date.current internally to keep track of oldest record,
      # How can i alter the return of Date.current for it to return eg yesterday
    else
      trim_data
      @data[key] = [yield, Date.current]
    @data[key].first
  end

  def trim_data
    if @data.size >= DATA_SIZE_LIMIT
      @data.delete(@data.sort_by{|k,v| v.last}.first.first)
    end
  end