Earthshine

Earthlight is the diffuse reflection of sunlight reflected from Earth's surface and clouds. Earthshine (an example of planetshine) causes the Moon's ashen light, the dim illumination of the otherwise unilluminated portion of the Moon by this indirect sunlight. Earthlight on the Moon during the waxing crescent is sometimes called "the old Moon in the new Moon's arms", while that during the waning crescent is called "the new Moon in the old Moon's arms".