Blue Moon Dates Table
| Year | Blue moon month(s) | Note |
|---|---|---|
| 1996 | July | - |
| 1999 | January and March | double year; February had no full moon |
| 2001 | November | - |
| 2004 | July | - |
| 2007 | June | - |
| 2009 | December | December 31 - a New Year's Eve blue moon |
| 2012 | August | - |
| 2015 | July | 19 Metonic years after 1996 |
| 2018 | January and March | double year; February had no full moon |
| 2020 | October | - |
| 2023 | August | - |
| 2026 | May | the most recent one |
| 2028 | December | December 31 - New Year's Eve, one Metonic cycle after 2009 |
| 2031 | September | - |
| 2034 | July | - |
| 2037 | January and March | double year; February had no full moon |
| 2039 | October | - |
| 2044 | August | - |
| 2047 | September | - |
| 2052 | May | - |
Twenty blue moons between 1996 and 2052, every one the second full moon to fall inside a single calendar month - the modern 'Pruett' definition - with the month list copied from the Blue moon reference's published chronology and the arithmetic visible underneath: twelve synodic months of 29.53 days beat the calendar year by about 11 days, so every 29 months or so a month can hold two full moons.
Bottom line: the most recent blue moon was May 2026, and there is none between that and December 2028 - which lands on December 31, making it a New Year's Eve blue moon, exactly one 19-year Metonic cycle after the December 31, 2009 one. Three years in the table - 1999, 2018, 2037 - manage two blue moons each, and in each of them February holds no full moon at all.
The rhythm, not the romance: the Metonic cycle - 19 solar years almost exactly 235 lunations - maps most entries onto a counterpart 19 years later, same month or one over, which is why July 2015 answers July 1996 and 2028 repeats 2009's New Year's Eve. It is bookkeeping you can plan a decade around, and the table goes out to 2052 so you can.
How to use
- Pick any year from 1996 to 2052 - most years answer 'no blue moon', and years between events show the gap you are in, such as the 31-month wait between May 2026 and December 2028.
- The counter always shows days to the December 31, 2028 blue moon - the next one on the calendar - whatever year is selected.
- This table uses the calendar definition only (second full moon of one month, UTC-anchored months); the seasonal 'Maine rule' version - the third of four full moons in a season - falls on different dates and is noted in the FAQ.
Frequently asked questions
When is the next blue moon?
December 31, 2028 - a genuine New Year's Eve blue moon, the second full moon of December 2028, and one Metonic cycle (19 years) after the December 31, 2009 one. Before that, the most recent was May 2026; the 31-month gap between the two is longer than average but not record-breaking.
What is a blue moon, exactly?
Today it usually means the second full moon within one calendar month - the definition this table lists. An older 'Maine rule' counts the third full moon of four in a single astronomical season, and a 1946 magazine misreading of that older rule is how the popular calendar-month meaning spread. There is no official definition; like the black moon and supermoon pages on this site, the rule here is: pick one, state it, stick to it.
Does a blue moon actually look blue?
No - it is an ordinary full moon in an ordinary month; the color is pure calendar bookkeeping. The moon can genuinely look blue, but only when the air itself filters the light: after major volcanic eruptions such as Krakatoa in 1883, or vast forest-fire smoke plumes, droplets roughly one micron wide scatter red light and leave the moon visibly bluish for weeks.
Why do 1999, 2018 and 2037 each have two blue moons?
Because January's full moon arrives in the month's first days, so a second fits on January 30-31 and the next lunation - about 29.5 days later - lands in early March, skipping February entirely. Those same years are the mirror image of the black moon calendar's February 2033, which holds no new moon; a two-full-moon January and a no-full-moon February travel together.
How often is a blue moon, and can the pattern be predicted?
About once every 29 months on average, though clumped: none at all in some stretches, two in years like 1999. The 19-year Metonic cycle - 235 lunations within two hours of 19 solar years - repeats the pattern faithfully enough that July 2015 answers July 1996 and the 2028 New Year's Eve repeats 2009's, which is how this table can list dates to 2052 with confidence.