Every now and then the moon is gigantic in the sky. Does anyone know when this occurs?

This phenomenon is know as, Looming. On rare occasions the atmospheric conditions have a magnifying effect, it is also common at sea, a cost line will appear to much closer than it actually is.

The moon is always the same size in the sky. Really! What changes is your perception, judging the size of an object relative to the nearest neighboring structure. So when the moon is on the horizon, behind a tree or building it looks HUGE. There are time lapse photographs on the web that have measured the size of the moon and the only difference is some small amount of light scattering due to the refractive index of the amount of atmosphere that the light travels through on the horizon compared to the amount of atmosphere when it is straight up.

Now if you are asking when the full moon occurs, this is once every 28 days.

This is known as "the Moon Illusion" and occurs whenever the Moon (or Sun) is low in the sky, close to the horizon. This occurs twice a day for both the Sun and Moon: when they rise and when they set. The image in E.T. was trick photography. Photographers have to shoot sunrise, sunset, moonrise, and moonset with long telephoto lenses to try to match the Moon Illusion, since a photograph doesn't capture the effect naturally.

The size of the moon on a video or movie depends on how much magnification is used to shoot it.

The actual apparant size of the moon never changes enough to be easily noticeable by the naked eye. When it is low on the horizon, it can sometimes seem to be larger, but that is only a trick of the mind. Our mind thinks that things in the sky near the horizon are further away than things in the sky above us. As such, since the moon's apparant size is still the same on the horizon, our mind makes is think it must be much larger in order to appear the same size and be what we think is much further away.

Don't forget that Moon does not have a perfect orbit around the Earth either.It has an elliptical orbit.It has an apogee the point it's at farthest from the Earth and a perigee at it's closest point to the Earth.

the moon has little gravity.earth do has gravity and the gravity causes the moon to be around earth. as earth's gravity is more than moon's,there the moon is oval.let me xplain u,wat happens when u pull a balloon full of air from one side? it bulges out on one side.the same way the earth is pulling the so called balloon "moon" so it looks large sumtimes from earth but if u see the moon in space from a distance u will know

It is the angle at which you are viewing. Don't know where you can find the dates. It is not actually closer. Notice that you do not have the same largest effect as the moon rises.

The moon looks bigger to us when it is closer to Earth, during perigee, also it looks bigger of course when it is full. Sometimes when there is a lot of light reflected off of it from the sun that makes it look bigger too.

http://www.moonconnection.com/apogee_perigee.phtml