The reason why it is dark outside during the nighttime hours is due to the rotation of the Earth on its axis, which results in different regions of the planet being exposed to daylight and darkness at different times.

Here's a simplified explanation:

Rotation of the Earth: The Earth rotates on its axis, which is an imaginary line passing through the North and South Poles. This rotation causes different parts of the Earth to face the Sun at different times.

Day and Night: As the Earth rotates, the side facing the Sun experiences daytime, while the opposite side experiences nighttime. When a specific region is turned away from the Sun, it receives less direct sunlight, making it appear dark.

Location and Time Zone: The exact time that it becomes dark or light outside depends on your location on the Earth and the time zone you are in. Different time zones are based on the rotation of the Earth and help keep track of local times accurately.

So, when it is dark outside, it's because your region is currently facing away from the Sun due to the Earth's rotation. As the Earth continues to rotate, your area will eventually turn to face the Sun again, bringing back daylight.