my $start_dt = DateTime->new(
                    year       => $start_year,
                    month      => $start_month,
                    day        => $start_day,
                    hour       => $start_hour,
                    minute     => $start_minute,
                    second     => $start_second,
                    nanosecond => 000000000,
                    time_zone  => "$start_tz"
                );