What else could make ghost stories scarier than telling them under an all-lit rare Halloween "blue moon"?
According to the Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA), the first full moon this month occurred last Oct. 2, and the second full moon will be on Oct. 31 at 10:49 p.m.
"Since the lunar cycle is 29 days and most months have 30-31 days, we eventually find a situation where a full moon occurs at the beginning and the ending of the same month," it explained.
For more than half a century, whenever two full moons appear in a single month, which happens on average every 2.5 to three years, the second full moon is called a "blue moon," PAGASA said.
However, it pointed out that the term "blue moon" has nothing to do with the actual color of the moon.
But there are times that a moon appears with a tinge of blue in certain atmospheric conditions, such as when there are volcanic eruptions or when exceptionally large fires leave particles in the atmosphere, it said.
According to the annual American periodical Farmers' Almanac, "a full moon on Halloween occurs roughly once every 19 years—a pattern known as the 'Metonic Cycle.'"
After the 2020 Halloween full moon, a 100 percent-illuminated Halloween full moon may be observed again in 2039, 2058, 2077, and 2096.