Time Zone Difference
Each 15 degrees of longitude equals one hour.
Formula
Variables
Example
45° of longitude corresponds to 45/15 = 3 hours of time difference.
How it works
Earth turns once in about 24 hours, and the full 360° of longitude are covered during that rotation. Dividing 360° by 24 gives 15° per hour, so a longitude gap can be converted into an approximate time gap by dividing by 15. This works best for standard time zones, not for exact local solar time or places with unusual political time zone boundaries.
When to use it
Use this when you need to estimate the time difference between two locations based on their longitudes, such as in map work, navigation, or geography problems. It is especially useful for comparing local times across countries or regions.
Worked example, step by step
Find the time difference for a longitude difference of 75°. Δt = Δlongitude ÷ 15° Δt = 75° ÷ 15° Δt = 5 So, the time difference is 5 hours.
Common mistakes to avoid
- Forgetting that the answer is in hours, not degrees
- Using latitude instead of longitude
- Assuming every place follows the calculated time exactly, even when real time zones are irregular
Did You Know?
Each 15° of longitude equals one hour — the reason the globe is divided into 24 time zones.
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