# File lib/dbi/sql.rb, line 56
      def as_timestamp(str)
        return nil if str.nil? or str.empty?
        ary = ParseDate.parsedate(str)
                  begin
                          time = ::Time.gm(*(ary[0,6]))
                          if ary[6] =~ /^(\+|\-)\d+$/
                                 diff = ary[6].to_i * 60 * 60
                                 time -= diff
                                 time.localtime
                          end 
                          DBI::Timestamp.new(time)
                  rescue ArgumentError
                          nil
                  end
      end