Understanding Time Zones - How to Convert Time Between Countries
Time zone conversion explained. Learn how UTC offsets work, how daylight saving time affects conversions, and how to easily find the right time in any country.
What is a Time Zone?
A time zone is a region of the Earth that observes a uniform standard time. The world is divided into 24 main time zones, roughly corresponding to 15-degree bands of longitude. Each zone is defined by its offset from Coordinated Universal Time (UTC) — the global time standard based at 0° longitude (the Prime Meridian through Greenwich, London).
How UTC Offsets Work
Every time zone is expressed as UTC+ or UTC− followed by a number of hours (and sometimes minutes). For example:
- UTC+0 — London (GMT, winter time)
- UTC+1 — Paris, Berlin, Lagos (Central European Time)
- UTC+5:30 — New Delhi (Indian Standard Time)
- UTC−5 — New York (Eastern Standard Time)
- UTC−8 — Los Angeles (Pacific Standard Time)
- UTC+8 — Beijing, Singapore, Perth
How to Convert Between Time Zones
To convert a time from one zone to another, follow these steps:
- Find the UTC offset of the source time zone
- Find the UTC offset of the target time zone
- Calculate the difference between the two offsets
- Add or subtract that difference from the source time
Example: What time is it in New York when it's 3:00 PM in London?
London (UTC+0) → New York (UTC−5) = 5 hours behind
3:00 PM − 5 hours = 10:00 AM in New York
Example: What time is it in Tokyo when it's 9:00 AM in Lagos?
Lagos (UTC+1) → Tokyo (UTC+9) = 8 hours ahead
9:00 AM + 8 hours = 5:00 PM in Tokyo
The Complication: Daylight Saving Time (DST)
Many countries shift their clocks forward by one hour during summer months to make better use of daylight. This changes the UTC offset of affected zones, which means the time difference between two places changes depending on the time of year.
For example, New York is normally UTC−5 (EST), but during daylight saving time it becomes UTC−4 (EDT). London moves from UTC+0 (GMT) to UTC+1 (BST) in summer. This means the difference between London and New York can be either 5 hours (winter) or 4 hours (summer) depending on whether both, one, or neither location is observing DST at any given moment.
Important Time Zone Abbreviations
| Abbreviation | Full Name | UTC Offset |
|---|---|---|
| UTC / GMT | Coordinated Universal Time | UTC+0 |
| EST | Eastern Standard Time (US) | UTC−5 |
| EDT | Eastern Daylight Time (US) | UTC−4 |
| PST | Pacific Standard Time (US) | UTC−8 |
| IST | Indian Standard Time | UTC+5:30 |
| WAT | West Africa Time (Nigeria) | UTC+1 |
| CST | China Standard Time | UTC+8 |
| AEST | Australian Eastern Standard Time | UTC+10 |
Convert Time Zones Instantly
Use our free time zone converter to quickly find the equivalent time in any part of the world. No manual calculation needed.