Time zones are necessary for regulation of modern life in respect to trade, economy, communication and standardisation. In ancient times neighbouring towns had different times and a meeting at a distinct time was not easy to do. Later a kind of synchronisation of the time between distant locations was done e.g. by acoustical signals. Clocks were got more accurate over the time and the need of a standardised zone with the same time was the solution. But the Earth rotates and therefore more than one time zone is more practical. Therefore twenty-four time zones were set up which differing from neighbouring time zones by one hour but for some exceptions.