We have all experienced the headache of time zone differences. Whether it is travelling to another country, calculating the start time of an online meeting, figuring out when a favorite TV show is aired overseas, or simply trying to call our beloved ones abroad. Keeping track of different time zones around the world can often be a source of frustration. This often leads to one simple idea; why cannot we all just share the same time? To answer such a question, we need to understand first what time zones are and how this system works.
Time Zones
While the Earth makes its annual rotation around the Sun, giving us seasons as summer and winter, it also rotates on its axis once every 24 hours. Since people spread all over the planet, they do not face the Sun at the same time; the areas facing the Sun experience daytime, and those facing away experience night. Different countries sharing the same time set their clocks the same way, according to “time zones”, so people can have sunrise in the early morning hours and sunset in the evening hours, which is known as “localized times”.
Time zones are defined by imaginary lines, known as “meridians”, which stretch from the Earth’s North Pole to the South Pole and cross lines of latitude. Around the world, there are approximately 24 time zones, generally representing one hour of the day, and ideally setting their time one hour different from adjacent zones. This logic is derived from the fact that the planet is a sphere-like, which can be divided into 360 equal degrees/sections; each section, or time zone, is measured as 15 degrees wide, resulting in 24 sections/hours.
International Date Line
The Earth is split into eastern and western hemispheres of longitude, using an imaginary primary line known as the “Prime Meridian”. It is located at 0° longitude, running through Greenwich, England, where the system of 24-hour timekeeping originated and the time is called Greenwich Mean Time (GMT). As you go west from the Prime Meridian, you subtract an hour for every time zone you cross through, or conversely, you add an hour for every time zone you cross through as you go east.
Based on this concept, time travel is indeed a real thing; yet, it is not quite what you have probably read in books. Since the Earth does not go on indefinitely, you have to start over at a certain a point, and this is how the International Date Line (IDL) works. Opposite to the Prime Meridian lies the IDL, which is located roughly along the 180° line of longitude in the mid-Pacific Ocean. When you cross the IDL, you either gain or lose a whole day depending on your direction of travel; if you travel westward, you move to the next day, and if you travel eastward, you move back to the prior day.
A well-known example of real-world form of time travel is the Diomede Islands, also known as the Yesterday and Tomorrow Islands. The Russian “Big Diomede” (Tomorrow) and the USA “Little Diomede” (Yesterday) islands are separated by just 3.8 kilometers; yet, the former is almost a day ahead of the later, since they sit on opposite sides of the IDL. The simple act of looking to Big Diomede from Little Diomede, allows you to look into the future.
Interesting Facts
- Time zones are not always in straight lines; they often deviate from longitudinal lines to accommodate political and geographical borders.
- Large countries that span a vast geographical area have several time zones; for example, Russia has eleven time zones, and the USA has around six time zones.
- Several countries set their own times; for example, China technically could have five time zones, but the entire country follows a single time zone (China Standard Time).
China/Credit: timeanddate.com
- Most small countries follow the same time zone, even if part of them falls outside a meridian line, such as Belgium, Denmark, Lebanon, Singapore, and Switzerland, to simplify daily life, business, and communication nationwide.
- Some nations adapt a system that changes time zones by smaller increments instead of full hour, to align the national time more closely with the country’s local solar time at a central meridian; for example, India is 5 hours and 30 minutes ahead of GMT.
Now, after understanding how the system of time zones works, we might still wonder: why cannot we simply adopt a unified global time? This would seem easy, especially when we consider that some countries already adjust their clocks to certain time zones, or forward and backward for Daylight Saving Time. In our next article, we will closely examine this concept and explore its potential advantages, challenges, and complexities it would cause.
References
bbc.co.uk
earthobservatory.nasa.gov
learningresources.com
livescience.com
momatos.in
oceanservice.noaa.gov
pacioos.hawaii.edu
sciencemuseum.org.uk
timeanddate.com
Cover image by Freepik