    # File lib/active_support/core_ext/date/calculations.rb, line 79
            def advance(options)
              d = self
              d = d >> options.delete(:years) * 12 if options[:years]
              d = d >> options.delete(:months)     if options[:months]
              d = d +  options.delete(:weeks) * 7  if options[:weeks]
              d = d +  options.delete(:days)       if options[:days]
              d
            end