Understanding the Blue Moon – Updated July 2015

The idea or concept that two Full Moons in a month is what defines a Blue Moon is a mistake, according to this Sky and Telescope article. The article says the original definition of a Blue Moon referred to 4 Full Moons in one season. The article also indicates a season is defined as the time between a Solstice and Equinox or an Equinox and Solstice. (See Table below)

From the perspective of Solstices and Equinoxes, there are four seasons in a year and generally three Full Moons occur in each season. This means there are usually 12 Full Moons per year. This is why the word month comes from the word Moon or Moonth, because it take 29.5 days for the Moon to return to another Full Moon phase (or any Moon phase for that matter). This suggests that our secular calendar actually does recognize that they are at least 12 Full Moons each year. Looking at this from the perspective of the Gregorian Calendar that was instituted in 1582 the years that have two Full Moons in a month are the years that also have 13 Full Moons in a calendar year.

In the year 2012 there are 13 Full Moons in the Calendar year from January 1 to December 31 with two Full Moons in the month of August. In 2013 there are only 12 Full Moons in the calendar year from Jan 1 to Dec 31. However, from December Solstice 2012 to December Solstice 2013 there are 13 Full Moons with four Full Moons in one season, happening between the June Solstice and the September Equinox.

Based on the above article in Sky and Telescope describing the original meaning of once in a Blue Moon as having four Full Moons in one season, the year 2013 most closely fits the definition. In addition to the four Full Moons in a season, 2013 also features two consecutive Full Moons in the same sign. On July 22 there is a Full Moon at zero Aquarius and on August 21 there is another Full Moon at 28 Aquarius. More about this in a moment.  (Also see table below)

Different Types of Blue Moons

Night sky watcher Tomsajinsof the blue moon taken in NYC, August 31, 2012. http://www.space.com/17354-blue-moon-pictures-full-moons-august-2012.html

In more recent times, the term Blue Moon has been used to describe the occurrence of two Full Moons in a calendar month. This way of defining a Blue Moon comes from a 1940’s article that appeared in Astronomy magazine suggesting the definition of a Blue Moon was the second Full Moon in a calendar month. This is an event that occurs approximately every three years.

July 2015 featured 2 Full Moons, one on July 1 in Capricorn and the second on July 31 in Aquarius. The last time there were two Full Moons in a calendar month was August of 2012 and the next time it will happen is January 2 and 31 and March 1 and 31 of 2018 (due to February being a short month so there is actually no Full Moon in February of 2018).

This pattern recurs about every 33 months or 33 Full Moons so just under three years with of course the exception of 2018 due to February being a short month.

Interestingly, two Full Moons in a month, or four Full Moons in a season, occur with the same frequency about every 2.7 years. (See the tables below) However, four Full Moons in a season has greater astronomical significance than two Full Moons in a calendar month.This is because  the months as outlined in our Gregorian Calendar are NOT astronomically based but rather begin arbitrarily on a date called January 1 so our calendar begins at a time that is not connected to either a Solstice or Equinox. It is also not connected to the lunar cycle.

The Gregorian calendar does however fixate our awareness on a linear way of tracking time through days, weeks, months and years. These dates have been assigned names and numbers and it works brilliantly as a linear way of tracking time.

There is another speculation that the original term Blue Moon may have come from the bluish tinge the Moon gets when viewed through smoke. In this case, the theory is that someone saw the Moon appearing quite blue through the smoke of a large distant fire (like a forest fire) and therefore the term Blue Moon was a literal description of how the Moon looked. Naturally that would also be a rare occurrence. In fact, it would be the rarest occurrence of all the definitions of a Blue Moon.

Here is a 2012 YouTube from Nasa on Blue Moons produced by volcanos and fires. http://www.youtube.com/watch?v=4HRKl0fa2dg

Two Consecutive Full Moons in the Same Sign
There is another way the Full Moon (or any phase of the Moon for that matter) fits the 2.7 year pattern. This configuration isn’t talked about as much but is just as significant as the other patterns, and that is when there are two consecutive Full Moons in the same sign. This only occurs when the first Full Moon is in Zero or One degree of the sign and the next Full Moon is in 28 or 29 degrees of the same sign.

As already mentioned above, July 22, 2013 there is a Full Moon at 00 degrees and 16 minutes of Aquarius. The following month on Aug 21 there is another Full Moon at 28 degrees and 11 minutes of Aquarius. This exact configuration happened one day later in July and August of 2002 with the Moon very close to the same degrees that are occurring in 2013.

Note: This nearly exact recurrence is tracking the 19 year nodal cycle at its half way point. (A topic for another article)

Blue Moon Mystique
The common factor to all these variations of  a Blue Moon, either as seen through smoke, or the number of Full Moons in a season, or two Full Moons in a month, or two consecutive Full Moons in the same sign, is they captivate and inspire our imagination.

When we understand the pattern of what is happening then we can intentionally tune into the magic, getting the most out of the opportunity these Timings represent. One of the opportunities any Full Moon provides is a chance to experience greater illumination of our essential divine nature regardless of whether or not it is a so-called Blue Moon.

From the perspective that we inform the mysteries as much as they inform us, what we put our attention and intention on becomes meaningful. Since there is a lot of collective attention on the phenomenon of two Full Moons in a month, (even though its not astronomically significant) it has the effect of taking on greater significance as a result.

Noticing the Pattern
Below are tables of the various types of Blue Moon dates to ponder. These tables clearly show the pattern of about 2.7 years for all the above variations, except for the one that has to do with seeing the Moon through smoke.

One way to work with this information and the dates below is to notice if any of these Timings were especially significant in your personal experience. Also worth noticing is if there were significant events in the world that happened around any of the prior so-called Blue Moon times?

In tracking this personally, I had a profound experience with a group down in Peru during the December 2002 Full Moon – Blue Moon of four Full Moons in a season (see table below) that was beyond the beyond of anything I had experienced previously. (Here is a more mytho-poetic version of that time )

In July 2004, there were two consecutive Full Moons in a calendar month. At the time of the second Full Moon during another Full Moon ceremony I was a part of, I had an illumination about a personal situation that had been especially challenging. This Timing also coincided with a powerful Pluto transit to my natal Moon, so the Full Moon activation was a part of that cycle and it turned out to be a further catalyst for an initiatory process I was already experiencing, meaning the two factors were working together to help support my journey and may not have had anything to do with the fact that it was the second Full Moon of the month.

This suggests that knowing your cycles and participating in Full Moon ceremonies can help further what ever initiation cycles are going on for you. I have noticed the Full Moon often activates a personal part of my own chart regardless of whether it is a so-called Blue Moon.

The Full Moon Effect Lasts at least Three Days and 3 Nights
Experientially the Moon appears full for three nights, the day before, the day of and the day after the exact Full Moon. Shamanically speaking this suggests the potency of the Full Moon Window lasts for at least three days. Many cultures including the Hawaiians (Hawaiian Moon Calendar article) worked with every possible phase of the Moon in its 29.5 day cycle before it returns to a particular Moon phase and they considered the Moon to be in its full phase for 4 days and nights.

The Hawaiians use 29 and sometimes 30 phases of the Moon, giving each phase its own special name and indications like when it was a good time to fish, or to plant, or to get married, or to stay home.

Is 12 or 13 the Most Sacred Number of the Moon?
In recent years, there have been many articles and books claiming that the number 13 is the most sacred number for the Moon. However, the Moon actually intimately connects with the numbers 12, 13 and 19.

If you are tracking the Moon return to a certain zodiacal degree, say zero Capricorn, it will return to that degree every 27.3 days. If you divide 27.3 into 365 days in a year – the closest whole number is 13. That means the Moon will cross that point or any other starting point 13 times each year.

If you are tracking the Moon phases from Full Moon to Full Moon or any other phase (i.e. New Moon to New Moon or First Quarter Moon to First Quarter Moon) it returns every 29.5 days. If you divide 29.5 into 365 the closest whole number is 12. That is why there are 12 months (moonths) in a year.

It is important to realize the number 13 for the Moon is NOT what most people think it is. There are NOT 13 Full Moons every year regardless of whether you are tracking a calendar year, or a seasonal year – from one December Solstice to the next. Actually more often than not there are only 12 Full Moons a year. That is why both 12 and 13 are sacred numbers, or sacred patterns for the Moon.

Additionally, the 19 year pattern or cycle of the Moon is significant to our personal experience especially when we are turning 19, 38, 57, 76, and 95. This 19 year Moon cycle is related to Nodes of the Moon and the Eclipses…stay tuned for future articles on this subject. The point here is that there is more than one sacred number for the Moon, as the Moon has many patterns that are worth knowing and understanding, because these patterns do play out in our personal and collective experience.

Blue Moon Dates Based on 4 Full Moons in a Season
(13 Full Moons from Dec Solstice to the next Dec Solstice) 

2000 4th Full Moon in a  Season Mar 20, Apr 18, May 18, Jun 17
2002 4th Full Moon in a Season Sep 21, Oct 21, Nov 20, Dec 19
2005 4thFull Moon in a Season Jun 22, Jul 21, Aug 19, Sep 18
2008 4thFull Moon in a Season Mar 21, Apr 20, May 19, Jun 18
2010 4th Full Moon in a Season Sep 23, Oct 23, Nov 21, Dec 21 +eclipse
2013 4th Full Moon in a Season Jun 23, Jul 22, Aug 19, Sep 19
2016 4th Full Moon in a Season Mar 23, Apr 22, May 21, Jun 20
2018/2019 4th Full Moon in a Season Dec 22, Jan 21, Feb 19, Mar 19
2021 4th Full Moon in a Season Jun 24, Jul 24, Aug 22, Sep 20
2024 4th Full Moon in a Season Jun 22, Jul 21, Aug 19, Sep 18
2027 4th Full Moon in a Season Mar 22, Apr 20, May 19, Jun 18
2029 4th Full Moon in a Season Sep 22, Oct 22, Nov 21, Dec 20
2032 4th Full Moon in a Season Jun 23, Jul 22, Aug 21, Sep 19
2035 4th Full Moon in a Season Mar 23, Apr 22, May 22, Jun 20
2038 4th Full Moon in a Season Mar 21, Apr 19, May 18, Jun 17 +eclipse
2040 4th Full Moon in a Season Jun 24, Jul 24, Aug 22, Sep 20

13 Full Moons in Solar Year (Dec Solstice To Dec Solstice)
next occurs in 2016 (last occurrence was 2010 and 2013)

01. 2015 Dec 25 Cancer
02. 2016 Jan 23 Leo
03. 2016 Feb 22 Virgo
04. 2016 Mar 23 Libra eclipse
05. 2016 April 21 Scorpio
06. 2016 May 21 Sagittarius
07. 2016 Jun 20 Sagittarius
08. 2016 Jul 19 Capricorn
09. 2016 Aug 18 Aquarius eclipse
10. 2016 Sep 16 Pisces eclipse
11. 2016 Oct 15 Aries
12. 2016 Nov 14 Taurus
13. 2016 Dec 13 Gemini

Full Moon Dates Based on Two Full Moons in a Calendar Month

Nov 2001 2 Full Moons/Month November 1 and 30
Jul 2004 2 Full Moons/Month July 2 and 31
May 2007 2 Full Moons/Month May 2 and 31
Dec 2009 2 Full Moons/Month December 2 and 31
Aug 2012 2 Full Moons/Month Aug 2 and 31
Jul 2015 2 Full Moons/Month July 2 and 31
Jan 2018 2 Full Moons/Month January 2 and 31 with no Full Moon in February AND
March 1 and 31
Oct 2020 2 Full Moons/Month October 1 and 31

 Two Consecutive Full Moons In The Same Sign

(No Taurus, Gemini, Leo, or Cancer)

2000 Feb 19 00 Virgo 51 2000 Mar 20 29 Virgo 53
2002 Jul 24 00 Aquarius 18 2002 Aug 22 29 Aquarius 39
2005 Jun 22 00 Capricorn 51 2005 Jul 21 28 Capricorn 47
2008 Apr 20 00 Scorpio 43 2008 May 20 29 Scorpio 27
2010 Sep 23 00 Aries 15 2010 Oct 23 29 Aries 33
2013 Jul 22 00 Aquarius 06 2013 Aug 21 28 Aquarius 11
2016 May 21 01 Sagittarius 14 2016 Jun 20 29 Sagittarius 33
2019 Mar 21 00 Libra 29 2019 Apr 19 29 Libra 27
2021 Jul 24 01 Aquarius 26 2021 Aug 22 29 Aquarius 37
2024 Jun 21 01 Capricorn 07 2024 Jul 21 29 Capricorn 09
2027 Apr 20 00Scorpio 37 2027 May 20 29 Scorpio 14
2029 Aug 24 01 Pisces 12 2029 Sep 22 29 Pisces 57
2032 Jul 22 00 Aquarius 30 2032 Aug 21 28 Aquarius 34
2035 May 22 00 Sag 57 2035 Jun 20 29 Sag 20
2038 Mar 21 00 Libra 33 2038 Apr 19 29 Libra 29
2040 Jul 24 00 Aquarius 48 2040 Aug 22 29 Aquarius 53


  1. There are two New Moons in Cancer in 2009. Cancer is ruled by the Moon, so it is a significant event. Although your article focuses on Full Moons, the opposite is true as well – there will be two New Moons in the same month or sign in between when there are two Full Moons in the same month or sign. These events are just as important, if not more than Full Moons.

    During Full Moons, we have both classical planets, the Sun and the Moon, pulling on the Earth in opposite directions. However, during a New Moon phase those gravitational pulls are even greater when you have both the Moon and the Sun tugging on the Earth in the same direction.

    Just something to add to your article… <>


  2. Thank you Wayne it is true this works for all the Moon phases New Moon, Full Moon and the First and Last Quarter Moons as well. Plus as you mentioned when the Moon is Perigee (or closest to the Earth) the New Moon and Full Moon will have a greater affect on the tides and the weather patterns as was evidenced last summer in the summer of 2008 when we had several occurrences of these Moon phases near the perigee.

    I was in Wisconsin when they had all that mid-west flooding and tornadoes just after a Full Moon near Perigee that was also an out-of bounds Moon crossing Galactic Center. So that adds a whole other dimension to consider as well.

  3. The full moon effect is not 3, but 5 days, this because the moon is in the earths magnetosphere for 5 days (2,5 before and 2,5 after exact full moon)

    • Interesting, thank you for sharing and I am wondering where that information about the Moon being in the Earth’s magnetosphere for 5 days comes from as I would love to know more about it. I do know the Hawaiians actually consider the Moon to be Full for 4 days/nights. What I was speaking of in the article is that visually the Moon is Full for three Nights – so experientially the Full Moon is rising very full (with very little discernible difference) for at least 3 nights.

  4. Hi Cayelin! Im a long time student of the Arcane School started by Alice Bailey and there we follow the moon cycles in meditation. An the Tibetan master tells us that 2 days before the full moon is a time of purification to let in the energies of the sign the sun is in, the full moon day is a day of reception and concentration and the 2 day after are days were the energies are send out to the collective field. So one day I checked the astronomy behind that, and I find out that the moon is only inside the earths magnetosphere for the five fullmon days, and those days the energy from the sun can come in to the earths field without interference from the moon. Those days the moon is bombarded by particles that circulate in the earths field. I will try to find the link to the astronomy site were I found that information.

  5. Thank you Jan. Very cool! And I hope you can find the link as this would help explain the experience so many have around the effects of the Full Moon…

  6. Hi Cayelin… great article!!!

    For what it is worth the Metatronic Councils of Light told me many years ago, circa 1997, that energetically they consider a “Blue Moon” to be defined by the circumstance you outline under your heading above “Two Consecutive Full Moons in the Same Sign”.

    Simeon Chi’Ra

    • Thank you Simeon for that as a confirmation that it is far more significant to have Two Consecutive Full Moons in the Same Sign than in the same calendar month. 🙂

  7. Hi, Cayelin – I enjoy your newsletters and was glad to see you explain the difference between the true origin of the term blue moon and the more common (erroneous) interpretation in use today. The research I did for the July episode of my LOOKING UP cable tv show mentioned the source of the word “blue” as likely having morphed from the Old English word “belewe” meaning to betray. Each of the full moons had a name and a place in its season.

    When there was an extra full moon in winter, it affected the timing of Lent and Easter (which is defined as the first Sunday after the first full moon of spring). The “betrayer moon” (the third of the season) came too early to be the Lenten Moon and needed a different name or Christians would have to fast an extra month until Easter. (It’s easy to understand why no one wanted to do that!)
    Thus, a blue moon does occur in a season with four full moons but it is NOT the fourth full moon, rather the third in the season. This method keeps the seasonal full moon names on track.

    I also looked at the frequency of the two types of blue moons and found that because of time zone/international date line differences in our man-made calendars that the seasonal type of blue moons are actually a little more frequent than the two-in-a-calendar month variety.

    The seasonal type occurs five times in a dozen years (using the 3rd of 4 in season definition):
    Nov. 21, 2010 Aug. 20, 2013 May 21, 2016 May 18, 2019 Aug. 22, 2021

    In the same period, the twice-in-a-month type occurs only once EVERYWHERE (and this month is it):
    2009: Dec. 2 and 31 (except for parts of Asia, where the 2 full moons will be in Jan. 2010, on the 1st and 30th)
    2010: (only in Asia) on March 1 and March 30 (elsewhere the full moon is on Feb. 28)
    2012: (not in Asia) Aug. 2 and 31 (in the Far East, the second of these is on Sept. 1)
    2012: (Far East) Sept. 1 and 30
    2015: July 1-2 and 31 (EVERYWHERE)
    2018: Jan. 2 and 31 (except in Asia, where the full moon will be Feb. 1)
    2018: March 2 and 31 (except in the Far East and Pacific islands, where the full moon is April 1)
    2020: Oct. 1 and 31 (except in the Far East, where the full moon is Nov. 10

    So this month’s (though erroneous) blue moon is kind of a “once in a blue moon” phenomenon. Enjoy! Janet Booth

  8. I’d like to preface this by saying that while I am very fascinated by astrology, I don’t know or understand as much as I’d like to. Beyond that, after reading such thoughtful and intellectual comments, I feel bad asking such an ignorant and personal question!

    But…. while nothing has ever been easy in any way for me, I have had a pretty rough year. Then came July this year. my birthday is July 7 and I have systematically had terrible birthdays. Despite the fact that the 6 days before my birthday were incredibly stressful, painful, etc. I had an ok birthday! (Only because i expected very little and laid even lower) There were no bad surprises, which was the only good surprise I’ve had this month!

    other than that, this has been the longest month imaginable. I am not exaggerating when I say that there have been but only a few days this month where something seriously crappy didn’t happen!

    So my question is, how can I have had the worst month imaginable, when apparently this is the time for a cancer to shine? the hailstorm that my life has become has left me numb to it all, which helps take the emotion out of things, but at the end of the day, I’m desperate for answers!! Anyone? Anyone?

    • Hi Ali,
      So sorry to hear about your challenges. Without knowing your chart the one thing I can say is with a July 7 birthday it is very likely you are in a Pluto cycle and that can be extremely challenging to say the least. What you describe is classic Pluto. The saying “what doesn’t kill you makes you stronger” was invented for these types of cycles.

      The good news is they do end and on the other side of them life is often magical and amazing. I am speaking from experience when I have been in Pluto and events were so beyond my control and horrible I wished I could die. When the cycles were over the gifts were beyond anything I could imagine and I was so happy I survived. So hoping this is helpful.

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