The following is by Mark Hollabaugh, author of The Spirit and the Sky: Lakota Visions of the Cosmos (Nebraska, 2017). His book examines nineteenth-century Lakota astronomy and its connection to their spirituality. The cover art, Majestic Guardian by Lakota artist Sandy Swallow, shows lunar phases seen over Bear Butte.
Once in a Blue Moon
The Moon was in the news in January. This year 2018 began with a full moon on January 1 and there will be another full moon on January 31. Almost everyone has heard the expression “Once in a blue moon,” meaning that some occurrence is a rare event. The second full moon in a calendar month is a blue moon but the Moon does not look blue. What is unusual about early 2018 is that there will be another pair of full moons in the month of March, specifically on March 1 and March 31. This happens this year because intervening February has only 28 days and the lunar phase cycle is 29.5 days.
The January 1 full moon appeared slightly larger and brighter because the Moon was near its closest approach to the Earth, what astronomers call perigee. This is the so-called supermoon, but many astronomers would simply call it a near-perigee full moon. These supermoons can occur every 413 days. The Moon generally looks larger when it is near the horizon and many observers will perceive the rising supermoon as larger than usual. However, supermoons are so close in appearance to an average lunar apparition that the publicity surrounding supermoons may be much ado about nothing.
The Moon was important to the Lakota who referred to the full moon as Wí mimá, round moon. For example, in the late nineteenth-century the Lakota preferred to hold the Sun Dance during a full moon near the time of the summer solstice in June. Lakota clothing is sometimes adorned with crescents representing the Moon. Moon images appear in Lakota winter counts often with other celestial objects. One of the most magnificent meteor shower displays in history occurred on the morning of November 13, 1833. An icon from the Flame Winter Count for this Leonid meteor shower in 1833 shows a crescent moon with numerous star-like meteors.
The new moon occurred on 11 November 1833, so it is not surprising that the waxing crescent (Wílechala) was drawn with the meteors.
Like other Native Americans, the nineteenth-century Lakota relied on the Moon to keep track of the passage of time. They had names for each lunar month that was keyed to something happening in the environment around them. For example, January was the “hard moon” or “tree popping moon” reflecting the hardships of winter life on the plains or limbs snapping due to ice and snow laden branches. (For a complete list of Lakota months according to six diverse sources, see pp. 90-91 in The Spirit and the Sky.)
This year illustrates an important feature of Lakota time telling on an annual basis. There actually are 13 full moons in the calendar year 2018. Two in January, none in February two in March, and one each in the following nine months. Our modern calendar of twelve months is based on the Gregorian calendar reform of 1582. It is not easy to reconcile a lunar calendar with the solar calendar which keeps step with the seasons. The problem arises because there are 29.5 days from new moon to new moon and there are 365.25 days in a solar year. Hence, there are about 12.4 lunar months per solar year. About every three years, an additional month is needed to keep the lunar and solar calendar synchronized, so that the months coincide with the natural events they describe.
The Lakota added a leap month, Tanin śni wi, discernible-not moon or lost moon, to keep the environmental descriptions of the months aligned with the annual progression of the seasons based on the Sun. James Walker, physician at Pine Ridge in the late 1800s to early 1900s, noted “The Discernible-not moon sometimes appeared and sometimes did not, and no one could tell for certain whether it had appeared or not until the seasons showed that it had appeared.” German explorer Johann Georg Kohl noted a similar conundrum among the Ojibwe living in the Lake Superior region: “I grant that all the Indians cannot divide the months with equal correctness; and it is often comical to listen to the old men disputing as to what moon they are in.”
So, this year you can tell your friends there are 13 “moons” and tell them about the Lakota Tanin śni wi lunar month. Perhaps a comical argument will ensue.
 Painting on wood by Mark Hollabaugh, based on Garrick Mallery, Picture-Writing of the American Indians (New York: Dover, 1972. Originally published in the Tenth Annual Report of the Bureau of Ethnology, 1888–1889. Washington, DC: Smithsonian Institution, Bureau of American Ethnology, 1893), 723.
 James Walker, Lakota Society, Edited by Raymond J. DeMallie (Lincoln: University of Nebraska Press, 1982), 122–23.
 Johann Georg Kohl, Kitchi-Gami: Life among the Lake Superior Ojibway (London: Chapman and Hall, 1860. Reprint, St. Paul: Minnesota Historical Society Press, 1985), 120.