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What Is a Black Moon?

There are several definitions of a Black Moon. The next one is on August 21, 2017 and will cause a total solar eclipse nicknamed the Great American Eclipse.

Illustration image

The first days after a New Moon.

A Waxing Crescent Moon is visible the first days after a New Moon.

©bigstockphoto.com/mr. Smith

Black Moon is not a well known astronomical term. In recent years, the term has been made popular by social media, astrologers, and followers of the Wiccan religion.

No Single Definition

There is no single accepted definition of a Black Moon. The term has been commonly used to refer to any of the following phenomena associated with the New Moon:

  • 2nd New Moon in a calendar month: These Black Moons are the most common ones, and they occur about once every 29 months. Because of time zone differences, the month they happen in can vary, like the Black Moon in September 2016 (US) or October 2016 (UK).

  • 3rd New Moon in a season of 4 New Moons: These Black Moons are a little rarer, and occur about once every 33 months. Astronomers divide a year into 4 seasons - spring, summer, fall (autumn), and winter. Usually, each season has 3 months and 3 New Moons. When a season has 4 New Moons, the 3rd New Moon is called a Black Moon. This is the exact counterpart to the original definition of a Blue Moon, except that Blue Moons are Full Moons.

  • A calendar month without a New Moon: About once every 20 years, the month of February does not have a New Moon. This can only happen in February, as this is the only month which is shorter than 1 lunation. When this occurs, both January and March will have 2 New Moons, instead of the usual 1 New Moon. The next Black Moon by this definition will occur in 2033, while the last one was in 2014. Because of time zone differences, these Black Moons may not happen all over the world. For instance, there is a Black Moon in the most western parts of the US in February 2022, but not in Europe or Australia.
  • A calendar month without a Full Moon: About once every 20 years, February does not have a Full Moon. Instead, January and March have 2 Full Moons each. The next Black Moon by this definition will occur in 2018, while the last one was in 1999. Because of time zone differences, these Black Moons may not happen all over the world.

Invisible New Moon

New Moon is the moon phase when none of the Moon's surface is illuminated and we cannot see the Moon at all from Earth.

However, 2–5 times a year, the New Moon comes between Earth and the Sun, causing a solar eclipse. The New Moon, or at least a part of it, is then visible as a silhouette in front of the Sun.

Great American Eclipse

Total Solar Eclipse
A New Moon totally eclipsing the Sun.
The Black Moon in August 2017 will cause a total solar eclipse aka the Great American Eclipse.
©bigstockphoto.com/JohanSwanepoel

On August 21, 2017, a Black Moon will cause a total solar eclipse.

This particular Black Moon is the 3rd New Moon in a season with 4 New Moons, which makes it rare combination.

It will be visible, weather permitting, in a path spanning all across the United States from the East Coast to the West Coast, which has earned it the nickname the Great American Eclipse.

What will the Great American Eclipse look like where you are?

Ritual Significance

Black Moons hold special significance to people who practice certain forms of Pagan religions and who believe certain actions become more potent when performed on the night of a Black Moon.

Topics: Astronomy, Moon, Calendar, Months

Recent/Upcoming Black Moons

YearDate/MonthType
2017Aug 21Third New Moon in a season with four New Moons
2018FebCalendar month without a Full Moon
2019Jul 31Second New Moon in a single calendar month
2020Aug 18Third New Moon in a season with four New Moons

Black Moons can vary by time zone. Dates above are based on the local time in Washington DC. Change location

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The Moon

  1. What Is a Supermoon?
  2. The Moon Phases
  3. The Moon's Effect on Tides
  4. What Is a Micro Moon?
  5. How Can Full Moon Be in the Daytime?
  6. Is a Blue Moon Blue?
  7. The Moon's Orbit
  8. The Far Side of the Moon
  9. What Is a Black Moon?
  10. What Are Moonbows?
  11. Full Moon Names
  12. Taking pictures of the Moon

Moon index

Moonrise & Moonset Times

Moon Distance

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