Time Zone Offset
Hours difference from longitude difference.
Formula
Variables
Example
15° = 1 hour
How it works
Because Earth rotates once in about 24 hours through 360°, it turns 15° of longitude each hour. This means places farther east or west from each other can have different local times, and the time difference is found by dividing the longitude difference by 15. The result tells you how many hours to add or subtract between the two locations.
When to use it
Use this when comparing local time between two places on Earth, especially in geography, travel planning, and map-based questions. It is also useful for estimating time differences before applying specific time zone rules or daylight saving changes.
Worked example, step by step
Find the time difference between two cities that are 45° apart in longitude. Δt = Δlongitude / 15° Δt = 45° / 15° Δt = 3 Final answer: the local times differ by 3 hours.
Common mistakes to avoid
- Forgetting that east is ahead of west in local time
- Using latitude instead of longitude
- Treating the result as exact clock time without checking time zones or daylight saving rules
Did You Know?
The world's 24 time zones were standardised only in the 1880s, driven by the spread of railways.
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