That's a great question! The full moon itself is technically just a moment in time, when the moon is exactly opposite the sun in the sky. But we call the entire night when the moon appears fully illuminated a "full moon," so in that sense, it lasts for about a day.

Here's a breakdown:

* Full moon moment: This is the exact point in time when the moon is fully illuminated. It lasts for a very short period.

* Full moon night: The entire night when the moon appears full is considered the full moon. This usually spans roughly 24 hours.

So, while the full moon itself is a brief moment, we generally consider the entire night (or even the entire day, depending on your location) leading up to and following that moment as the "full moon".