how long is the blue moon

A blue moon, defined as the second full moon occurring in a single calendar month, lasts for about the same duration as a full moon phase. The full moon phase itself roughly lasts for about one night, appearing fully illuminated for several hours around the peak moment, as the moon's cycle is about 29.5 days per full cycle between new moons. Specifically, the "blue moon" is not a special moon with longer duration; it simply means the full moon occurs twice in one month due to the lunar cycle being about 29.5 days while calendar months are typically 30 or 31 days. The visible full moon phase typically spans several hours each time it occurs. In summary, a blue moon lasts for the duration of a full moon, which is a few hours around the moon's peak fullness on that night, similar to any other full moon.