Not sure where I first saw this:

A plane enters Darwin air space and, without identifying itself, asks traffic control for the local time.

Traffic control replies ‘If you’re an international flight, it’s 1600 hours. If you’re a domestic flight, it’s 4 o’clock. If you’re a local, the big hand is on the 12 and the little hand is on the four. If you’re a bush pilot, it’s Wednesday’.