Telling Time: The Moon and the Messiness of Calendars

One place where the motions of the earth and its tilt make themselves known in our everyday lives is in the use of calendars and monitoring of the seasons. For example, the first calendars made use of the regularity of the moons phases, a rather obvious pattern visible to the naked eye.

The Blanchard Bone Plaque depicting a series of moon phases carved into bone: Found in Abri Blanchard in the region of Dordogne, France, dated 25,000 to 32,000 BCE.

Unfortunately, lunar calendars are not especially easy to use in practice (if precision is expected) because the synodic (phase) period of the moon is 29.5 days*, and there are not a whole number of lunar cycles in a tropical (season-based) year of 365.25 days. The first issue was handled by most lunar calendars by alternating months of 29 and 30 days, the second by occasionally adding an extra or intercalary month to keep the lunar calendar in time with the repetition of the seasons. In this way, these calendars are more accurately called luni-solar calendars, as they depend on cycles of both the moon (phases) and sun (seasons). An example is the Jewish calendar. Hanukkah does not occur on the same date every year because it follows lunar months, but it never drifts from winter into autumn because of the addition of the intercalary month on a regular basis.

Different cultures handled the insertion of intercalary months using different rules; for example, this is why Chinese and Tibetan New Year do not always occur on the same date, but are sometimes (as is the case as 2012) one lunar cycle apart.

The other possibility is that you stick with a strictly lunar calendar and ignore the tropical (solar year). Over time your holidays will drift relative to the seasons (because your "year" is too short). This is what happens with the Islamic calendar, causing celebrations such as Ramadan to occur earlier and earlier each Western calendar year (moving backwards from winter to autumn to summer to spring and then to winter again).

In Western Culture the switch from a lunar-based calendar to one strictly based on the revolution of the earth around the sun was made with the Julian calendar (sponsored by Julius Caesar) in 46 B.C. With the minor changes made after Caesar's death we came to have a 12-month calendar of 365.25 days, with months of 30 and 31 days (with the exception of February). This calendar was adopted by the Catholic Church and widely used in Europe until the Gregorian reformation in the 16th century that changed the rules used to calculate leap years. Today the Gregorian calendar is the international standard. Clearly calendars have a rich historical and cultural history but are messy things in practice.

In recent years, one particular calendar has been the source of much anxiety and misunderstanding. According to Mayan scholars, December 21, 2012 marks the end of baktun 13, part of one of many cycles noted in Mayan calendar systems. The term "systems" is more accurate than "calendar," as the Maya had a number of different calendars for different uses, for example a 260-day ritual calendar and a 365-day seasonal calendar. Despite the fact that this does mark the end of one cycle, there is nothing in Mayan tradition to suggest that they thought the world would come to an end on this date. In fact, there are predictions for events far into the future past this date.

Lunar months (in both true lunar and luni-solar calendars) generally begin with the start of the moon's cycle, or with the new moon. But you can't see the new moon (unless it is covering the sun in a solar eclipse). Most lunar months today are therefore determined through computations rather than observations. Two exceptions are the Karaite Jewish calendar and the Islamic calendar. What does this all have to do with Middle-earth? Continue your journey here to find out.

*This is actually an average. It does vary slightly because the moon's orbit is not a perfect circle.


 Enclosed images belong to their respective owners and no copyright infringement intended. The text of The Hobbit and The Lord of the Rings belong to the Tolkien Estate and quotations are enclosed here for educational purposes only. Permission granted to use all original enclosed materials here for educational purposes. Original material written by Kristine Larsen, Central Connecticut State University.