Aviation Logistics Knowledge Lecture – Time Zone and Time Calculation

Hello everyone, this time let’s talk about time zones. Friends may think that this time it is about geography. In fact, this time there is really a lot of geographic knowledge involved. But don’t ignore these knowledge points. In air transportation, geographic knowledge is very important. To know the geographic location of different destinations, calculate flight time, etc., we need to use geographic knowledge. So, let’s talk about this geographic knowledge point in combination with the airlift industry.

 

Before getting into this topic, let’s review the basics. First, the earth is round. Then, the earth travels from west to east, and revolves around the sun from west to east. Finally, there are virtual latitude and longitude lines on the earth. The vertical line is the longitude line (naturally, it is divided into east-west longitude), and the horizontal line is the latitude line (naturally, it is divided into north-south latitude). These three sentences are not nonsense. They are said to let everyone review the correct perception again, because if these perceptions are wrong, then it is meaningless to talk about time zones, time, and seasons.

 

Due to the rotation of the earth, the alternation of night and day occurs, and due to the revolution of the earth, the alternation of the seasons occurs. Therefore, day and night are opposite in the east and west hemispheres, and four seasons are opposite in the north and south hemispheres. Geographically, in order to facilitate the calculation of time, scientists have divided the earth into 24 virtual time zones, each spanning about 15° of longitude. Between each time zone, the difference is one hour (ignoring the daylight saving time algorithm). In the following calculations, we use the northern hemisphere as an example.

 

Internationally, the time at the Greenwich Observatory in the United Kingdom is called “Greenwich Mean Time”. The longitude that passes through the Greenwich Observatory is called the “prime meridian”, and this is where 0 o’clock begins. From Greenwich, each time zone eastward (crossing 15° of longitude) moves forward one hour in time. For each time zone you go west, you move back one hour in time. In layman’s terms, when it is 0 o’clock in the UK, it is 8 o’clock in the morning in China. Because China is located in the East Eighth District, in the time zone calculation, eight hours need to be added to Greenwich Mean Time. This is why, in addition to the expression “East Eight District”, it can also be expressed as “+8” district. Greenwich Mean Time used to be called GMT (Greenwich Mean Time), but now it is generally referred to as UTC (Coordinated Universal Time).

 

You can refer to the picture below to have a more intuitive understanding of the time zone (click the picture to see a larger image). Of course, time zones are geographical divisions. According to China’s land area, China actually spans 5 time zones (East Fifth District to East Ninth District), but the time throughout China is unified. This is for the convenience of management, implementing a time zone within a unified country region and ignoring the behavior of geographic time zones is no problem. For example, when it is 9 am in Urumqi, it is also 9 am in Taipei. But there are exceptions. It seems that the United States (if I remember correctly, the United States should span 4 time zones – the West Fifth District to the West Eighth District), because the geographical area is too large, it is inconvenient for the national unified time, so within the United States, different Regions will have different times. What Eastern Time, Western Time, Pacific Time, etc., I will not explain them one by one.

Well, now everyone has a basic understanding of the difference in time between different places. We’re back to the times we’ll encounter when we’re air freight. Since we do international air freight, we often encounter cross-time zone shipments. Then, we need to calculate the time in different time zones. Let’s look at a simple one first. For example, when a plane flies to FRA, it is 8:00 am local time. So what is the Chinese equivalent? With the time zone concept mentioned above, we can know that Germany is located in the East 1st District, which is 7 hours slower than China (East 8th District), so when the FRA is 8:00 in the morning, China has already passed 8:00, so the time needs to be Push forward 7 hours, which is 2 o’clock in the afternoon of the same day.

 

At the same time, we need to pay attention to the flight timetable issued by general airlines, if the origin and destination are not in the same time zone, then unless otherwise specified, the departure time and landing time written on the timetable are displayed in local time ( Local Time, abbreviation: LT). I randomly intercepted the flight times of PVG-AUH and HKG-FRA on the official websites of EY and LH, respectively.

 

It can be seen from the picture that the departure and landing times of the two flight schedules are based on LT local time as the standard. So when you see the flight schedule in the future, if there is no explanation, you know that it is all about local time. If it is displayed in Greenwich Mean Time, it will generally indicate UTC time. But it is rarely written like this. If you want to ask why, it is because it is inconvenient to look at.

 

Now let’s discuss how to convert flight time. In fact, as long as we know the concept of time zone, it is not difficult to calculate the method of flight time. Specifically, there are three methods, but in fact, all three methods are inseparable from each other, and the reason is the same. Method 1: Convert all times to Greenwich Mean Time. The second method: convert all times to origin time. Third method: Convert all times to destination time. Then, after the time is unified, the flight time can be obtained by subtracting the landing time from the take-off time.

 

It happens that the above two timetables show the takeoff, landing time and flight time respectively. Let’s try to convert. Taking LH8089 as an example, the takeoff time is 7:20am in HKG, which is equivalent to 1:20am in FRA (FRA is located in East 1st District, so seven hours should be subtracted from Hong Kong time). Arrived at FRA at 13:30. So the flight time is 12 hours and 10 minutes. Look, does Duration also say 12:10? Simple, right? Friends, you can also try to convert the flight time of the EY flight to see. If you guys are like me and are not very good at math, then I will teach you a simple and rude method: counting! hand! ! refer to! ! !

 

Be careful not to miss that +1 when looking at the timetable. +1 means one more day. For example, the flight LH8459 in the picture above took off at 23:20 in the evening of HKG. The time to get to the FRA is 5:30am the next day. So when +1 appears, remember to add one day to the original time.

 

But if it is a trans-Pacific flight, you must remember that the time will be reduced by one day after conversion. Note, only available for west-to-east transpacific flights. Because in the Pacific, there is a virtual line called the International Date Line. As soon as this line is crossed from west to east, the date is immediately reduced by one day. Conversely, if the line is crossed from east to west, the date is immediately incremented by one day. The International Date Line is the black line shown in the image below. He is actually the 180° longitude, which should be a straight line in theory, but it is also extremely tortuous due to the problems of administrative regions and national boundaries.

 

Well, that’s all for the knowledge of time zones, I hope it helps everyone. Finally, I also share a list of time zones in various parts of the world found on Wikipedia. See you next time, Ciao!