They all have half a time zoneWhile time zones are regularly set up in hour increments, a few places have time zones that differ by 30 (and one, by 45) minutes. So, Tehran is 8.5 hours ahead of New York, for example, in UTC+3:30. And Kathmandu is UTC+5:45.
For the examples in the puzzle: Labrador, Canada is UTC-3:30, Bombay is UTC+5:30 and Darwin Australia is UTC+9:30. Beaver, USA varies in time zone (depending on which Beaver), but always is UTC-*.00.