Why Can We See the Moon During the Day?

The moon is above the horizon for roughly half of every day, whether the sun is up or not. You notice it less in daylight because it has to compete with the bright blue sky. But during the right phases, it reflects enough sunlight to stand out as a pale white disc. The sky is bright because the atmosphere scatters sunlight in all directions. The moon is visible because it reflects enough sunlight to beat that background brightness. It is not as dramatic as it is at night, but it is bright enough to see when the angle is right. Phases determine the timing. A full moon rises around sunset and sets around sunrise, so it is mostly a night object. A new moon is too close to the sun's glare. Quarter and crescent phases create the common daytime moon, especially in the afternoon or morning.