With modern NTP servers (Network Time Protocol) synchronisation is made easy. By receiving a signals from GPS or radio signals such as MSF or WWVB, computer networks consisting of hundreds of machines can easily be synchronised together, ensuring trouble free networking and accurate time-stamping.
Modern NTP time servers are reliant on atomic clocks, accurate to billions of parts of a second, but atomic clocks have only been around for the last sixty years and synchronisation has not always been so easy.
In the early days of chronology, clocks mechanical in nature, were not very accurate at all. The first time-pieces could drift by up to an hour a day so the time could differ from town clock to town clock, and most people in the agricultural based society regarded them as a novelty, relying in stead on sunrise and sunset to plan their days.
However, following the industrial revolution, commerce became more important to society and civilisation, and with it, the need to know what the time was; people needed to know when to go to work, when to leave and with the advent of railways, accurate time became even more crucial.
In the early days if industry, workers were often woken for work by people paid to wake them up. Known as ‛knocker-uppers.’ Relying on the factory time-peice, they would go around town and tap on people’s windows, alerting them to the start of the day, and the factory hooters signalled the beginning and end of shifts.
However, as commerce developed time became even more crucial, but as it would take another century or so for more accurate timepieces to develop (until at least the invention of electronic clocks), other methods were developed.