The most common reason why passengers miss their flights is because they misunderstood the travel times on their itinerary. Each airline does ‘their own thing’ when it comes to how the flight times should be written on the Passenger’s Itinerary Receipt, whether in civilian/12-hour or military/24-hour clock notation.

Times quoted in civilian/12-hour clock can become misleading especially if the am or pm is left off. Someone with a 12:00 o’clock flight could easily show up for a 12:00 noon or 12:00 midnight of one day or 12:00am of another day’s flight. Or if you are told that your flight is at 1:00am and you need to check in at the airport at 11:00pm the day before, you could easily become very confused.

The military/24-hour clock is generally used in specialist areas such as aviation, navigation, meteorology and hospital to name a few, as it prevents ambiguity. In fact, in most countries, computers show the time in 24-hour notation.

Airlines reservations systems give military/ 24-hour clock times as it leads to less confusion. The airline or travel agents are trained to read the 24-hour clock. In some airlines, reservations are booked and ticketed showing the times in 24-hour clock notation, however, the flight times will convert to 12-hour clock on the passenger’s itinerary.

12-Hour versus 24-Hour Time

The main difference between the 12- hour and the 24-hour clock time is how the hours are written. The 12-hour clock uses numbers 1 to 12 to identify each of the 24 hours in a day. To clearly identify the hours before 12 noon, a.m. is written and for the hours after 12 noon, p.m. is written.  Example, 10:00am would be ten o’clock in the morning and 10:00pm would be ten o’clock in the evening.  In the 24-hour clock time, the hours are numbered from 00 to 23. Midnight can be expressed as 00:00 if referring to the beginning of the day or 24:00 if referring to the end of a given date.  In other words, 24:00 of one day is the same time as 00:00 of the following day.

The minutes and seconds of both the 12-hour and 24-hour clock times are written in the same way. Times for the 24-hour clock are written in the form hh:mm or hh:mm:ss, where h=hour, m=minute and s=seconds. Sometimes the colon is removed from between the hours and minutes, so the format can also be hhmm or hhmm:ss. The hour however is always written as a 2-digit number hence any hour before 10 is written with a zero before it, example 06:33 or 09:10. When converting from 12-hour to 24-hour clock times and vice versa, the minutes and seconds do not change.

Itineraries are always written in Local Times.

When reading your itinerary, it is important to remember that the flight times given are local times. The departure time is the time of the city from which you depart and the arrival time is the time of the city of arrival. Any time difference between the two cities would already have been taken into consideration. Example, between London, England (Europe) and Kingston, Jamaica (Caribbean) there is a five (5) or six (6) hour difference depending on the time of year `and daylight saving time. Your itinerary will say departure time from London at 2:15pm/14:15, which is 02:15pm London time. The arrival time will say 5:45pm/17:45 which is Kingston time. Yes, your flight is eight and a half hours long, however the time difference has already been taken into consideration.

Whether your flight times are written in 12-hour or 24-hour clock times, the onus is on you to get it right. Examine your Passenger Itinerary Receipt as soon as you get it. If you do not understand your flight times, be sure to ask. One common misunderstood reading is arrivals times that appear with a (+1) at the end. This means that you will arrive one day after the flight departures.

If you miss your flight because you misunderstood the flight times there is a cost to make changes. It could also involve additional cost for hotel, food and transportation if there is no other flight on the same day to your destination at the time when you arrive at the airport.

The Conversion Chart below will help you convert from the 24-hour to the 12-hour Clock and vice versa.

Chart