What is Time Zone? How to Calculate Time Zones for Vietnam, Internationally

As you know, the Earth is spherical in shape, revolving around the Sun. Thus, one hemisphere illuminated by the sun experiences daylight while the other remains in darkness, experiencing nighttime. This variation in daylight and darkness across the globe results in different times in each country or locality. Hence, the concept of time zones arises. To understand in detail what time zones are and how to calculate them for Vietnam and internationally, don't overlook this article.

How many Time Zones are there? Time Zones of Various Countries Compared to Vietnam

1. What is a Time Zone?

What are UTC and GMT time zones? A time zone (local time) is understood as a region on Earth that shares a common standard time. Currently, the formula for calculating time zones for each country exists to help people easily determine the time zones of each country by dividing the Earth into equal parts, each part one hour apart from the prime meridian (international time when the meridian passes through the Royal Observatory in Greenwich, England). Therefore, the time zone in the United Kingdom is UTC + 0.

GMT time zone (Greenwich Mean Time) is the mean solar time annually based on the Sun passing through the Prime Meridian each day. Whereas UTC time zone (Coordinated Universal Time) is a time zone proposed by the International Bureau of Weights and Measures to serve as a reference for determining standard time. Since the GMT time zone is defined by the United Kingdom and has many limitations, it has been converted to the UTC symbol, meaning Coordinated Universal Time. However, the spoken language of some countries still uses GMT.

2. How to Calculate Time Zones in Vietnam and Worldwide

What is Vietnam's Time Zone, and How do Other Countries Compare? As mentioned earlier, the international formula for calculating time zones is each part one hour apart from the prime meridian. The time zone of each country in the world is determined by the deviation from the prime time. Specifically:

Formula for calculating local time on Earth:

T_m = T_o + M

Where:
- T_m: time zone.
- T_o: GMT time.
- M: order number of that time zone.

Knowing the time zone at a longitude, you can easily determine the local time and vice versa:

TM = T_m +/- D_t

Where:
- D_t: the time difference between the longitude of the time zone and the longitude for which the time needs to be determined.
- +D_t: In the Eastern Hemisphere.
- -D_t: In the Western Hemisphere.

As Vietnam lies on longitude 7, our time zone is +7. You often see Vietnam's time zone denoted as GMT +7 or UTC +7. Simply determine the country you are researching at which longitude to calculate its time zone. To make it easier for you to determine the time zones of countries, refer to the time zone conventions of the following countries and regions:

Time zones of countries and regions around the world

From these time zones, you can determine how many hours apart different countries are. For example:
If the current time in the UK (UTC +0) is 8 a.m. on Tuesday, then:
- The time in Vietnam, Thailand... (UTC +7) is 1 p.m. on Tuesday.
- The time in the US (UTC -5) is 3 a.m. on Tuesday.

We hope that with the information shared above about what Time Zones are, how to calculate the Time Zone of Vietnam and other countries around the world, it has provided you with useful information. From there, you can set the appropriate local time if you have the opportunity to travel abroad.