Blue Moon Answers!

The following are answers for question #15 from 2004 - It's A Leap Year! web page.

15. GO LOONEY!
Is there a "Blue Moon" during this Leap Year (2004)? Answer: Yes (July 31)
(Blue Moon Calculator)

Research and learn information about "Blue Moons".
There are 2 contrasting explanations for when a "Blue Moon" occurs!
(//"Blue Moon"//) (Sky & Telescope) (Maine Farmers' Almanac: Four full moons in a season)

The modern definition uses the term Blue Moon to mean the second Full Moon in a single calendar month. Using this definition, February is the only month that never has a Blue Moon because the average interval between Full Moons is about 29.5 days. This interval is always greater than the length of February, even in a leap year. (Blue Moon Frequency)

The older, traditional definition of a Blue Moon (
Maine Farmers' Almanac) uses the term to mean the third Full Moon in a season which has four Full Moons. Normally a season has three full moons. Using this definition, February occasionally does have a Blue Moon! (Four full moons)

external image frog4.gifHow many leap years during the past 100 years have had a "Blue Moon"?
(a.) Write down the years that were leap years since 1900. Make a table to record your information.
(//Online Conversion//)
(b.) Draw a circle around the ones that have a "Blue Moon"?
(Phases of the Moon) (Maine Farmers' Almanac: Four full moons in a season)
(c.) How many did you find? Which years?


Leap Years
(since 1900)

Blue Moon/Date
"Modern" Blue Moon Definition

Blue Moon/Date
Maine Farmers' Almanac

1904
Yes (Mar. 31)
No
1908
No
No
1912
Yes ( May 30)
No
1916
No
No
1920
No
No
1924
No
Yes (Feb. 20)
1928
Yes (Aug. 31)
No
1932
No
Yes (Feb. 22)
1936
Yes (Sept. 30)
No
1940
No
Yes (May 21)
1944
Yes (Oct. 31)
No
1948
No
Yes (May 23)
1952
Yes (Dec. 31)
No
1956
No
Yes (Aug. 21)
1960
No
No
1964
No
Yes (Nov. 19)
1968
No
No
1972
No
Yes (Nov. 20)
1976
No
No
1980
Yes (March 31)
No
1984

No
1988
Yes (May 31)
No
1992
No
No
1996
No
No
2000
No
Yes (Feb. 19)
2004
Yes (July 31)
No



TOTAL
9 Blue Moon Leap Years
8 Blue Moon Leap Years

external image frog4.gif When was the last year that had 2 "Blue Moons"? Answer: 1999 (January/March)
(Double Blue Moons) (List)

Was it a Leap Year? Answer: NO
(//Online Conversion//)

external image frog4.gif When is the next year that will have 2 "Blue Moons"? Answer: 2018 (January/March)
(Double Blue Moons) (List)

Is it a Leap Year? Answer: NO

external image frog4.gif How often does a double blue moon occur? Answer: About 4 years per century
(Double Blue Moons)