calendar_month.rb

class CalendarMonth
  extend ActiveModel::Naming

  attr_accessor :start_time, :end_time

  FORMAT = '%Y-%m'

  def initialize(date_string = nil)
    if date_string.blank?
      now = Time.now
      self.start_time = now.beginning_of_month
      self.end_time = now.end_of_month
    else
      self.start_time = DateTime.strptime(date_string, FORMAT)
      self.end_time = start_time.end_of_month
    end
  end

  def to_param
    start_time.strftime(FORMAT)
  end

  def previous
    CalendarMonth.new((start_time.to_date << 1).strftime(FORMAT))
  end

  def next
    CalendarMonth.new((start_time.to_date >> 1).strftime(FORMAT))
  end

  def days
    tutorials = Tutorial.for_month(self)

    (start_time.to_date..end_time.to_date).map do |date|
      tutorials_this_day = tutorials.select do |tutorial|
        tutorial.starts_at.to_date == date
      end

      CalendarDay.new(:date => date, 
                      :tutorials => tutorials_this_day)
    end
  end

  def to_s
    I18n.localize(start_time, :format => :month)
  end
end