my ( $intotal, $outtotal, $i );
    foreach my $value ( @{ $data } )
    {
        $start += $step;
        my ( $minute, $hour, $day, $month, $year ) =
          ( localtime( $start ) )[ 1, 2, 3, 4, 5 ];
        $month += 1;    # Why does localtime give month -1?
        my $dt = DateTime->new(
                                year   => $year,
                                month  => $month,
                                day    => $day,
                                hour   => $hour,
                                minute => $minute
        );
        next unless $span_set->contains( $dt );
        $i++;
        $in_total  += $value->[ 0 ];
        $out_total += $value->[ 1 ];
    }
    # Now go off and work out averages / percentages etc...
    # Build a HoH and exit the for loop.
}
# Output some purty HTML.