Yesterday, Today, Tomorrow

xday.rb

#!/usr/bin/env ruby

class Time
  WEEKDAYS = %w[ Sunday Monday Tuesday Wednesday Thursday Friday Saturday ]

  def day_before_yesterday
    xday -2
  end
  
  def yesterday
    xday -1
  end
  
  def today
    xday 0
  end
  
  def tomorrow
    xday 1
  end
  
  def day_after_tomorrow
    xday 2
  end

  private
 
  def xday offset
    WEEKDAYS[(Time.now.wday + offset) % 7]
  end
end