Question

why doesn't eclipse occur on every full moon day or every new moon day

Answer 1

The moon takes about a month to orbit around the Earth. If the moon orbited in the same plane as the ecliptic – Earth’s orbital plane – we would have two eclipses every month. There’d be an eclipse of the moon at every full moon. And, two weeks later, there’d be an eclipse of the sun at new moon for a total of at least 24 eclipses every year.

Answer 2

A lunar eclipse occurs when Moon enters the Earth's shadow.A solar eclipse occurs when the Moon comes in between the Sun and 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.