date_calculator.rb

# This class calculates the current year given an origin day
# supplied by a clock chip.
#
# Author:: Armando Fox
# Copyright:: Copyright(C) 2011 by Armando Fox
# License::  Distributed under the BSD License
#
class DateCalculator
  #
  #  Create a new DateCalculator initialized to the origin year
  # * +origin_year+ - days will be calculated from Jan. 1 of this year
  #
  def initialize(origin_year)
    @origin_year = origin_year
  end
  #
  # Returns current year, given origin year and days since origin year
  # * +days_since_origin+ - number of days elapsed since Jan. 1 of origin year
  #
  def current_year_from_days(days_since_origin, this_year = @origin_year)
    if days_since_origin <= days_in_year(this_year)
      return this_year
    else
      return current_year_from_days(days_since_origin - days_in_year(this_year),
        this_year + 1)
    end
  end

  def days_in_year(year) # :nodoc:
    365
  end
end