General Mathematics · Earth geometry · demo

Fifteen degrees is one hour

Earth turns 360° in 24 hours, so 15° of longitude is one hour. Move a city off Greenwich and watch the clocks.

Greenwich meridian city meridian sun (noon at 0°)

Drag to orbit · scroll to zoom

Clocks

Greenwich

12:00

Local solar

18:00

Controls

90°E
12:00

Working

The time difference is the longitude difference divided by 15 — because a full turn is a full day.