Daytime is the hours when the sun is above the horizon, filling the sky with light. It's the opposite of nighttime. Daytime begins at sunrise, when the sun first appears over the eastern horizon, and ends at sunset, when it disappears in the west.

The length of daytime changes throughout the year. In summer, daytime stretches longer, giving you more hours of sunlight for playing outside, while winter days feel shorter and darkness comes earlier. At the equator, daytime and nighttime stay nearly equal year-round, but near the North and South Poles, daytime can last for months during summer and almost disappear during winter.

People use daytime as an adjective too: daytime television, daytime hours, or a daytime phone number (meaning when someone can be reached during business hours). Most schools, stores, and offices operate during daytime because humans naturally feel more alert and active when it's light outside. Our bodies have internal clocks that respond to sunlight, which is why you probably feel sleepier at night and more awake during the day.