In 2020, we’ll have three eclipses in one lunar month – the period of time between successive new moons or full moons – in June and July 2020. This time period during which eclipses are possible is also called an eclipse season. We won’t have three eclipses in one eclipse season again until the year 2029.
The year 2020:
The last time we actually had three eclipses in the span of one lunar month (the time period between successive new moons or full moons) was in the year 2018. It started with the Friday the 13th supermoon solar eclipse on July 13, 2018, and concluded with the solar eclipse of August 11, 2018:
July 13, 2018: Partial solar eclipse
July 27, 2018: Total lunar eclipse
August 11, 2018: Partial solar eclipse
So how often do we get three eclipses in one month? Let the investigation begin …
Three eclipses in one calendar month. Every calendar year has at least four eclipses – two solar and two lunar. More rarely, we have five, six or even seven eclipses in a single year. But four eclipses per calendar year is the most common number. A solar eclipse always comes within approximately two weeks of a lunar eclipse, and usually in a single pair (one solar and one lunar). Then, generally, another pair of eclipses (one solar and one lunar) comes some six months later.
According to NASA eclipse expert Fred Espenak, three eclipses fall in the same calendar month only 12 times during the five-century span from 1801-2300. Six times there are two solar eclipses and one lunar eclipse in one calendar month. Six times there are two penumbral lunar eclipses and a total (or annular) solar eclipse in one calendar month.
The last time we had three eclipses in a calendar month was in July 2000, when two partial solar eclipses bracketed a total lunar eclipse:
July 1, 2000: Partial solar eclipse
July 16, 2000: Total lunar eclipse
July 31, 2000: Partial solar eclipse
(We wish to state parenthetically that these three eclipses happened exactly one Saros period – or exactly 223 lunar months – before the eclipses of July 13, 27, and August 11, 2018.)
Previous to July 2000, the last time three eclipses took place in one calendar month was in March 1904, when two penumbral lunar eclipses bracketed an annular solar eclipse.
March 2, 1904: Penumbral lunar eclipse
March 17, 1904: Annular solar eclipse
March 31, 1904: Penumbral lunar eclipse
After July 2000, three eclipses will next occur within one calendar month in December 2206:
December 01, 2206: Partial solar eclipse
December 16, 2206: Total lunar eclipse
December 30, 2206: Partial solar eclipse
Three eclipses in one lunar month. Some might argue that the calendar month is an artificial constraint. It might be more appropriate to use a lunar (or synodic) month, which is a natural unit of time. A lunar month refers to the time period between successive new moons, or successive full moons.
Although it is rare for three eclipses to happen in the same calendar month, it’s not that uncommon for three eclipses to occur in one lunar month. In fact, from the years 2000-2050, the three-eclipses-in-one-month phenomenon takes place a total of fourteen times. Six times, the lunar month features two solar eclipses and one lunar eclipse (2000, 2011, 2018, 2029, 2036 and 2047). Eight times, the lunar month presents two lunar eclipses and one solar eclipse (2002, 2009, 2013, 2020, 2027, 2031, 2038 and 2049).
Three eclipses last took place in one lunar month in the year 2018:
Previous to 2018, three eclipses last took place in one lunar month in 2013:
April 25, 2013: Partial lunar eclipse
May 10, 2013: Annular solar eclipse
May 25, 2013: Penumbral lunar eclipse
After 2018, three eclipses in one lunar month will next occur in 2020:
June 5, 2020: Penumbral lunar eclipse
June 21, 2020: Annular solar eclipse
July 05, 2020: Penumbral lunar eclipse
Catalog of lunar eclipses 2001-2100
Bottom line: In one calendar month, three eclipses are rare. But in one lunar month, three eclipses are more common. From 2000-2050, it happens 14 times.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.