Worked example 1
It is 14:00 in London (UTC+0). What time is it in Tokyo (UTC+9)?
- Tokyo is 9 hours ahead.
- 14:00 + 9 hours = 23:00.
Answer: 23:00 the same day
Geography · Intermediate
Time zones explained, with worked examples
Because the Earth turns, noon happens at different moments around the world. Time zones divide the world so local clocks roughly match daylight.
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- 2See it worked
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Before you start
Who it's for and what to know first
Adding and subtracting hours on a 24-hour clock.
Learn it
How it works
- The Earth turns 360° in 24 hours, so every 15° of longitude is about one hour.
- UTC (Coordinated Universal Time) is the reference, close to GMT in the UK in winter.
- Places east of the UK are usually ahead (later); places west are behind (earlier).
- To convert: find the difference in hours, then add if the other place is ahead or subtract if behind. Watch for crossing midnight into the next or previous day.
- Daylight saving time moves clocks by an hour in summer in many countries, and not all countries change on the same dates. For real travel, check a current world clock.
Worked example 2
It is 03:00 on Tuesday in London (UTC+0). What time is it in New York (UTC−5)?
- New York is 5 hours behind.
- 03:00 − 5 hours goes back past midnight.
- 03:00 → 00:00 is 3 hours, then 2 more → 22:00.
Answer: 22:00 on Monday
Try it online · print it · check it
Practice questions
Tips
Common mistakes
- Adding when the place is behind — remember east is ahead.
- Forgetting to change the day when crossing midnight.
Last reviewed: 25 September 2026