# File lib/dbi/utils/timestamp.rb, line 71
      def to_s
         string = sprintf("%04d-%02d-%02d %02d:%02d:%02d",
             @year, @month, @day, @hour, @minute, @second) 

         if @fraction
            fraction = ("%.9f" % (@fraction.to_i / 1e9)).
                        to_s[1..-1].gsub(/0{1,8}$/, "")
            string += fraction
         end

         string
      end