If you have ever looked at a train ticket or flight schedule and wondered why the departure time is written as 18:45 instead of 6:45 pm, there is a practical reason behind it. Railways and airlines rely on the 24-hour clock to make schedules more precise, standardised and easier to understand.
Unlike the 12-hour clock used in everyday conversations, the 24-hour system gives every minute of the day a unique time between 00:00 and 23:59. This is particularly important in transport, where even a small misunderstanding over AM or PM can affect schedules and operations.
Why railways moved towards standardised time
The need for standardised time became increasingly important with the expansion of railway networks in the 19th century. Before standard time was widely adopted, different towns could follow their own local or sundial time.
This created obvious difficulties for railway operations. A train travelling between places could encounter different local times along its route, making it harder to coordinate arrivals, departures and connections.
Ravi Gosain, president of the Indian Association of Tour Operators, explained that the railway network played an important role in making standardised time increasingly necessary.
The problem with the 12-hour clock
The 12-hour system divides the day into two cycles, meaning the same number can refer to two different times. For example, 6:30 could mean either 6:30 am or 6:30 pm.
In normal conversation, the AM or PM distinction is usually clear from context. But transport schedules deal with thousands of passengers and operations, making ambiguity more risky.
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The issue can become particularly confusing around midnight, early-morning departures and late-night arrivals. The 24-hour clock removes this uncertainty by assigning every time a distinct position within the day.
Why airlines also use the 24-hour format
Aviation has an additional reason for relying heavily on precise timekeeping. International flights operate across different countries and time zones, requiring pilots, air traffic controllers and airport ground staff to coordinate accurately.
The 24-hour format makes communication more straightforward because there is no need to clarify whether a stated time falls in the morning or evening.
For aviation operations, Coordinated Universal Time, or UTC, is also used as a common reference to avoid confusion caused by different time zones. Passenger-facing flight schedules, however, may display local departure and arrival times.
Why 18:45 is clearer than 6:45 pm
Under the 24-hour system, the first two digits indicate the hour, while the final two indicate the minutes. The day begins at 00:00 and continues through 23:59.
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So, 18:45 refers specifically to 6:45 in the evening. There is no possibility of confusing it with 6:45 in the morning.
Similarly, 00:30 means half past midnight, while 12:30 refers to half past noon. This makes the system particularly useful for timetables, departure boards and operational communication.
A simple system designed to prevent major mistakes
For passengers, the 24-hour clock may initially look less familiar than the AM-PM format. But for railways and airlines, its biggest advantage is clarity.
With trains and flights operating across multiple routes and time zones, transport systems need a common and unambiguous way of communicating time. The 24-hour clock provides exactly that, reducing the scope for misunderstandings that could otherwise affect complex transport operations.