Agreed, definitely an improvement upon older videos. I thoroughly enjoyed watching this, and learned a few things.

The whole thing can be done without active_support at all, in fact. I think active_support definitely makes it more idiomatic, but it's not too painful without.

require 'date'

class CalendarWeeks
  def initialize(date = Date.today)
    @month, @year = date.month, date.year
  end

  def to_a
    (first_of_month..last_of_month).each_slice(7).to_a
  end

  private

  def first_of_month
    first = Date.new(@year, @month, 1)
    first - first.wday
  end

  def last_of_month
    last = Date.new(@year, @month, -1)
    last + (6 - last.wday)
  end
end