As Earth rotates, different parts of Earth receive sunlight or darkness, giving us day and night. As your location on Earth rotates into sunlight, you see the sun rise. ... Since different parts of Earth enter and exit daylight at different times, we need different time zones.

What would happen if we didn't have time zones?

“You would be more in tune with circadian rhythms, because the local times would be set according to the sun or local social habits, which would be geared by the sun more than time zones – there wouldn't be time zones so the problem goes away,” says Hanke.

Why is it important to have time zones?

The expansion of transport and communication during the 19th century created a need for a unified time-keeping system, and time zones were introduced. Time zones have a long history. Before clocks were invented, people kept time using different instruments to observe the Sun's meridian passing at noon.