class Date

# File lib/date_duration.rb, line 8
def self.duration(start_date, end_date)
  common_year_days_in_month = [ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
  start_date, end_date = end_date, start_date if start_date > end_date

  start_date_year, start_date_month, start_date_day = start_date.year, start_date.month, start_date.day
  end_date_year, end_date_month, end_date_day = end_date.year, end_date.month, end_date.day

  day_duration = end_date_day - start_date_day

  if (day_duration < 0)
    day_duration = common_year_days_in_month[start_date_month-1] - start_date_day + end_date_day
    end_date_month -= 1
  end

  if (end_date_month < 0)
    end_date_month += 12
    end_date_year -= 1
  end

  month_duration = end_date_month - start_date_month

  if (month_duration < 0)
    month_duration += 12
    end_date_year -= 1
  end

  year_duration = end_date_year - start_date_year

  duration_hash =  { :year => year_duration, :month => month_duration, :day => day_duration }

      duration_array = []
      ["year", "month", "day"].each do |key|
    value = duration_hash[key.to_sym]
    duration_array << value.to_s + " " + ((value > 1)? I18n.t(key.to_s.pluralize, :default => key.to_s.pluralize.to_s) : I18n.t(key.to_s, :default =>  key.to_s)).to_s if value > 0
  end
  duration_hash[:duration] = duration_array.join(" ").to_s
  duration_hash
end