date_range.rb

class DateRange
  def initialize(from, to, step)
    @from, @to, @step = from, to, step
  end

  def each
    current = @from
    while current < @to do
      yield(current)
      current += @step
    end
  end
end

dr = DateRange.new(1.year.ago, 1.week.from_now, 9.days)
dr.each { |dt| puts dt } ; nil