World Time is a general utility that allows you to check real-time time and time differences between cities in major cities around the world.
Time Difference: Select two cities to see the time difference.
Concept of World Time
World time is calculated based on the time differences caused by the Earth's rotation. Each time zone is set based on a 15-degree longitude interval, and there are a total of 24 time zones.
Standard Time Zone (UTC)
The standard time zone is defined as UTC (Coordinated Universal Time). UTC is based on the Greenwich Mean Time (GMT) of Greenwich, London, UK, where the Greenwich Observatory is located. The time zones of different countries are calculated as differences from UTC. UTC is used as a standard to precisely determine date and time, and it is the internationally recognized standard time.
For example, Seoul is in the UTC+9 time zone, meaning it is 9 hours ahead of UTC, while New York is in the UTC-5 time zone, meaning it is 5 hours behind UTC.
Principle of Time Zones
The Earth completes one rotation in approximately 24 hours. Based on this, the Earth is divided into 24 zones, with each zone having a time difference of 1 hour. For example, Seoul is in the UTC+9 time zone, so it is 9 hours ahead of London, which is in the UTC+0 time zone.
Reasons for Time Differences by Region
The time difference in different regions is influenced by the following factors:
- Longitude: Time zones are set based on longitude, with time advancing as you move eastward and slowing down as you move westward.
- Daylight Saving Time: Some countries use a system where they move the clock forward by 1 hour during the summer to save energy.
- Political Boundaries: Time zones can be artificially adjusted according to national borders or government policies.