The month of December will host a rare event on Thursday, a second full moon in the same month. This occurrence, popularly referred to as a “blue moon,” is relatively unusual, with widespread media attention, but no significant cultural impact, according to Kim Long, the author of The Moon Calendar and The Moon Book.
Blue moons occur on average every 2.7 years or every 33 months, and once every 33 full moons. In an average century, there are 37 blue moons. In 2010, there will be no blue moons, according to Long’s 2010 Moon Calendar, recently published.
The first use of the phrase “blue moon” in its modern sense dates to the mid-1900s. But at first, a blue moon referred to the fourth full moon in a season -- a standard three-month period including Spring, Summer, Fall, and Winter. In that application, a blue moon would occur just before a solstice or equinox.
Although western cultures place no real significance on blue moons, they do represent an unusual overlap with other, more ancient civilizations. Both Chinese and Hindu traditional lunar calendars rely on a periodic correction to keep the lunar months in sync with the solar year. This comes in the form of a “leap month,” in which extra days are added or subtracted to keep the systems aligned. For both the traditional Chinese and Hindu lunar calendars, these leap months always occur on the same month when there is a blue moon.
ABOUT THE MOON CALENDAR
The Moon Calendar has been published continuously since 1981. For 2010, it is newly designed in the form of a 28-page wall calendar, replacing the previous poster format.
CONTACT
www.themooncalendar.com
