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Time-keeping and synchronization of clocks has been a critical problem in long-distance ocean navigation.
Before radio navigation and satellite-based navigation, navigators required accurate time in conjunction with
astronomical observations to determine how far east or west their vessel traveled. The invention of an accurate
marine chronometer revolutionized marine navigation. By the end of the 19th century, important ports provided time
signals in the form of a signal gun, flag, or dropping time ball so that mariners could check their chronometers for error.

Synchronization was important in the operation of 19th century railways, these being the first major means of transport
fast enough for differences in local time between nearby towns to be noticeable. Each line handled the problem by synchronizing
all its stations to headquarters as a standard railroad time. In some territories, companies shared a single railroad track and needed
to avoid collisions. The need for strict timekeeping led the companies to settle on one standard, and civil authorities eventually abandoned
local mean solar time in favor of that standard.