This can be viewed twice in calendar years.
It's a Lunar Eclipse.
A lunar eclipse is the blocking of sunlight to the moon that occurs when Earth is directly between the sun and the moon. A lunar eclipse occurs when the Moon enters the Earth's shadow. A solar eclipse occurs when the Moon's shadow falls on the Earth. They do not happen every month because the Earth's orbit around the sun is not in the same plane as the Moon's orbit around the Earth.