Harvest Moon: Why It’s Special


September 13, 2019

With much being made of today’s fairly rare (approximately once every 20 years, on average) occurrence of a Friday the 13th Harvest Moon, many might be wondering: What is a Harvest Moon is anyway, and why is it so special?

What is A Harvest Moon?
Ever since Julius Caesar made the decision in 46 B.C. that the Roman Empire would employ a solar rather than a lunar calendar, our concept of what constitutes a month (think “moonth”) has been divorced from the regular cycles of the moon upon which it was originally based. The moon completes its cycle of phases about once every 30 days (29.531... days to be precise), but as part of the necessary compromise that a solar calendar requires, the months were standardized to varying lengths of between 28 to 31 days in order to make for a nice and even 12 months within each 365 day year. So most of us today measure time by the clock, by the calendar, and by the sun (in roughly that order), and the moon has been cut free to do what it does, with us only occasionally taking notice.

But for cultures following a lunar calendar (such as Native Americans), the annual cycles of the moon get much more attention. Just as we have names for each month in our calendar (based on old Latin terms over 2,000 years old), such cultures had a different name for each of the 12–13 lunar cycles that divide up the seasons. Though the name technically applies to the entire monthly lunar cycle, it is the full moon that naturally receives the most attention. Sometime during the Colonial period, a standardized list was established of names for each full moon occurring within a given calendar month. Most of the names in the list are probably of Native American origin, although, according to timeanddate.com, some might also have a basis in Anglo-Saxon or Germanic traditions. According to Farmers’ Almanac, the list is as follows:

January Full Moon: Wolf Moon
February Full Moon: Snow Moon
March Full Moon: Worm Moon
April Full Moon: Pink Moon
May Full Moon: Flower Moon
June Full Moon: Strawberry Moon
July Full Moon: Buck Moon
August Full Moon: Sturgeon Moon
September Full Moon: Harvest Moon or Corn Moon
October Full Moon: Harvest Moon or Hunter’s Moon
November Full Moon: Beaver Moon
December Full Moon: Cold Moon

The apparent confusion over what to call the full moon during the months of September and October arises from the definition of the Harvest Moon, which is: the full moon occurring closest to the Autumnal Equinox, which is around September 22. Since the closest full moon can occur within a range of approximately 15 days before or after that late September date, that means the Harvest Moon can fall in either September or October, hence the choice of names for those two month, depending on how the astronomy shakes out for that particular year.

What Makes A Harvest Moon Special?
For those of us living in the Northern Hemisphere, the Harvest Moon has another unique feature out of all the other full moons occurring throughout the year. Due to some rather complicated astronomical mechanics (if you want a more detailed explanation, check this out), the Harvest Moon’s position in the sky causes it to rise at close to the same time (at or shortly after sunset) for several evenings in a row. In the days of a pre-electric agricultural society, this provided a timely opportunity for farmers to work late into the night (as need dictated and weather allowed) in order to gather in the year’s harvest by moonlight.

Now you know the secrets of the Harvest Moon! So, whether you’re operating a combine late into the night, or strolling a city street, or driving down an interstate somewhere – or wherever you are – take a moment to look up and wonder at the big glow in the night sky!


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