Ideally, each time zone covers a 15-degree slice of the Earth that corresponds to the assigned time having the sun the highest in the sky at noon as opposed to another hour change, while keeping minutes synchronized. Of course, it often makes sense to slightly move off course from a straight north-south division, to make time synchronization more convenient within certain political boundaries; thus it makes sense for a column to have some areas with the time zone of the next column over.
Time zones in our world, however, go much wilder than these deviations. The following chart has the cases of more-than-one-hour-deviated time zones, fractional hour time zones, and time zones with more than 12-hour deviation from UTC pointed out.
Lord Howe Island, by the way, gets the distinction of being the only place in the world where Daylight Savings Time is a 30-minute deviation rather than an hour deviation.