How are daylight hours calculated?

• A. Time Between Sunrise and Sunset
• B. Time of Direct Sunlight Only
• C. Time of Sunrise Only
• D. Time of Day with No Cloud Cover

Answer: (A)

Daylight hours are the length of time the Sun is above the horizon. The day begins at sunrise, when the upper edge of the Sun first appears on the horizon, and ends at sunset, when it disappears. So the daylight duration is the difference between sunrise and sunset. This matters because daylight isn’t the same everywhere or every day: it grows longer in summer and shorter in winter, and at different latitudes. Also, the Sun’s apparent position is affected by atmospheric refraction, which makes sunrise occur a little before the Sun is geometrically on the horizon and sunset a little after.