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As if a pandemic, white supremacy, and an upcoming election weren’t spooky enough, 2020 also features a full “blue” moon on Halloween at 7:49 a.m. PT/10:49 a.m. ET. Though what is more unusual than a Blue Moon is having a full moon on Halloween — something to see only every 18–19 years. In all of the 21st century, we will only have six Halloween full moons: 2001, 2020, 2039, 2058, 2077, and 2096. If you combine a blue moon and a full moon on Halloween, it certainly adds extra astrological and witchy intrigue.
While several news outlets reported it has been 76 years since the last full moon on Halloween, this inaccuracy can confusion as with my calculations the last one was on October 31, 2001, at 9:43 p.m. PT. So those in later times zones missed it, though Pacific, Central, and Mountain Times have only waited 19 years.
The modern, more common meaning of blue moon — two full moons in the same calendar month occurs around every 2.7 years. In fact, the current usage of the term “Blue Moon” is relatively new in the past, when a journalist — obviously a man who wasn’t listening — misunderstood the phrase. However, what many don’t know is that there are several different types of blue moons, listed below. So while the phrase “once in a blue moon” means a rare occurrence, depending on the definition it can happen more or less frequently.
Here are the four types of Blue Moons (to my knowledge) with meanings that have evolved over the past century:
1) A seasonal blue moon or four full moons in a season instead of three. Between 1600 and mid 1960s, this was the prevailing definition. That last full moon was considered an added bonus and was determined by the Farmer's Almanac decided by growing seasons. Farming cycles often use meteorological seasons based on the annual temperature cycle and the 12-month calendar rather than astronomical seasons that focus on the position of the Earth's tilt in relation to the Sun. A true, blue moon is much more rare, around every three years, and apparently was misunderstood by a journalist in 1946 and then printed in a scientific magazine. I'm annoyed by this journalism, so I can't imagine how the interviewee must feel. According to the traditional meaning of blue moon, the most recent one occurred May 19, 2019 and then again next year on August 22, 2021.
2) Two full moons in the same calendar month. Though this is perhaps the most common usage of the term, it comes from a misunderstanding from a journalism in 1946 that then become more well-known. It also makes blue moons less rare because it happens more frequently, we had two in one year in 2018. What does make this type of full moon extra looney is the possibility of 13 full moons in one calendar year, as most years have 12.
3) Blue-colored Moon because of dust or smoke particles. The most science-y of the bunch and least predictable...not sure I want to see a blue moon of this type as it is linked to natural disasters. Earth's atmosphere contains smoke or dust particles and when in the air and the moonlight shines through them it can create a blue glow.
4) Two consecutive full moons in same astrological sign. Blue Moons don’t have astrological meaning, though this one would be rarer than a monthly Blue Moon. It would require two full moons while the Sun was in a specific zodiac sign…or 29.5 days apart.
While this weekend's witchy full moon deserves credit, combining the traditional meaning and modern meaning of Blue Moon in the same year...would have it's own kind of magic. The next time this happens would be in the year 2048 with a monthly Blue Moon on January 31 and a seasonal Blue Moon on August 23.