Why did the development of time zones make train schedule more reliable?

The fact that the trains were developed and that they allowed people to travel far very quickly were one of the reasons why time zones became necessary. Before the development of time zones, each town and city would have had its own time. However, as the train had to pass many towns quickly and regularly, it needed a strict schedule. This would have been impossible if the time of various towns was not unified. Therefore, by creating time zones, the train could anticipate its time of arrival and departure in each place, making schedules more reliable.