Lunar calendar: what it is, how it works and what it is used for

In this article we explain how a lunar calendar works, what types of lunar and lunisolar calendars exist, and what they are used for.​

What is the lunar calendar used for?

The most widely used calendar in the world, the Gregorian calendar, is a solar calendar system that incorporates months, because it evolved from the Roman calendar, which were lunar. Currently there is no correspondence between the months and the phases of the Moon.

The Gregorian solar calendar is the one in common and legal use in most countries, but the traditional lunar and lunisolar calendars are still used around the world to determine many religious holidays and national holidays.

For this reason, for example, the dates of Holy Week vary from year to year. Thus, Easter (last day of Holy Week) must be the Sunday immediately after the first full moon after the March equinox.

Other festivities that follow the lunar calendar are the Jewish, Chinese, Korean, Vietnamese or Mongolian New Years, among others; or the Islamic celebrations of Ramadan, Eid al-Fitr (Feast of the End of Fasting) and Eid al-Adha (Feast of Sacrifice).

A type of lunar calendar, the biodynamic calendar, is also used by farmers to track different tasks in the orchard based on the lunar phases. Likewise, the biodynamic lunar calendar is also used by many people to know what day it is best to cut their hair or wax according to the lunar phases or even to know what is best to cook taking into account the influence of the moon.

Since when do lunar calendars exist?

There is evidence of a lunar calendar outlined in the cave paintings of Lascaux (France) with 17,000 years old and in a bone cane found in the cave of Le Placard, 27,000 years old.

These findings are still controversial, as not all experts agree that the marks correspond to the representation of a lunar calendar.

In any case, historians such as Samuel L. Macey claim that The earliest uses of the Moon to measure time date back as far as 30,000 years.

The Sumerians were probably the first in developing about 6,500 years ago a calendar based entirely on the recurrence of the lunar phases. Each Sumero-Babylonian month began on the first day of visibility of the new moon.

How does a lunar calendar work?

The lunar calendar is essentially similar to the solar calendar. However, since the period of 12 lunations, a lunar year, is 354 days8 hours, 48 ​​minutes, 34 seconds, purely lunar calendars are 11 to 12 days shorter than the solar year.

In these calendars, the lunar months run through all the seasons of a solar year over the course of a cycle of 33 to 34 lunar years. The Islamic hijri calendar is an example of a strictly lunar calendar.

How long is a lunar month?

the lunar calendar It is structured by lunations. Since each lunation lasts approximately 29.5 days, it is common for the months of a lunar calendar to alternate between 29 and 30 days.

The duration of each lunar cycle varies slightly from the average value. Also, observations are subject to uncertainty and weather conditions. Therefore, to avoid uncertainty about the calendar, there have been attempts to create fixed arithmetic rules.

The average duration of the synodic month (the time it takes for an object, in this case, the Moon, to reappear at the same point in the sky with respect to the Sun, when observed from Earth) is 29.53059 days.

That’s why, lunar calendars alternate months of 29 and 30 days (sometimes called, respectively, “hollow” and “filled”).

When does a lunar month start?

The details of when the months start vary from one calendar to another: some use new, full, or waxing moons and others use detailed calculations.

In some lunisolar calendars, such as the Chinese calendar, the first day of a month is given by the astronomical new moon in a particular time zone.

In others, such as some Hindu calendars, each month begins the day after the full moon. Others are based on the first sighting of the crescent moon, such as the hijri lunar calendar.

Difference Between Lunar and Lunisolar Calendar

Most calendars described as “lunar” are in fact lunisolar calendars, because their months are based on observations of the lunar cycle, but collation is used (days are added to some months or a month every few years) to bring them into line with the solar year.

Examples of intercalated lunar calendars are the Hebrew or the Myanmar Buddhist calendar, which add a month every two or three years. Other lunar calendars are the Chinese, Vietnamese, Hindu and Thai calendars.

A very curious case is the lunisolar calendar adapted to natural phenomena related to the Moon. Its about banks islands calendarwhich takes into account when edible palolo worms amass on beaches in the last quarter of the lunar month, since the reproductive cycle of palolos (palola viridis) is synchronized with the Moon.

Types of lunar and lunisolar calendars

the chinese calendar

The traditional Chinese calendar is a lunisolar calendar. Although present-day China uses the Gregorian calendar, the traditional Chinese calendar governs holidays, such as Chinese New Year and the Lantern Festival, both in China and in overseas Chinese communities.

It is also used to select auspicious days for weddingsfunerals, removals or to start a business.

the hindu calendar

The Hindu calendar or panchanga is another lunisolar calendar. It is actually a set of calendars with differences to adjust the lunar and solar cycles, in synchronization with the seasons and in the use of intercalated months and days.

In general, lunar months are counted from new moon to new moon. Ordinary years are 354 or 355 days and leap years are 383, 384 or 385 days.

Gezer Calendar

Is a small limestone tablet with an early Canaanite inscription discovered in 1908 by Irish archaeologist RA Stewart Macalister in the ancient city of Gezer, 20 miles west of Jerusalem. It is commonly dated in the X century BC.

haida calendar

The Haida are an indigenous people, divided into two groups, the Kaigani (they live on Prince of Wales Island in Alaska) and the Haida (they live on the Queen Charlotte Islands in British Columbia, Canada). Its calendar is divided into two seasons (winter and summer) of six months each, with an occasional thirteenth month between seasons.

igbo calendar

It is the traditional calendar system of the Igbo people of the present Nigeria. The calendar has 13 months in a year (afo), 7 weeks in a month (onwa) and 4 market days in a week, plus an additional day at the end of the year, in the last month.

hijri islamic calendar

It consists of 12 lunar months in a year of 354 or 355 days. It is used to determine the appropriate days of Islamic festivals and ritualssuch as the annual fasting period (Ramadan) and the appropriate time for Hajj (pilgrimage to Mecca). In almost all countries where the predominant religion is Islam, the civil calendar is the Gregorian calendar, but the religious calendar is the Muslim one.

Javanese calendar

It is in force in Java together with the Gregorian and the Islamic. Although it has fallen out of use, it is still used for a large number of traditional ceremonies. It uses the same lunar year as the Islamic calendar, but incorporates another indigenous time cycle of 240 days.

Maori calendar (maramataka)

Maramataka means “the rotating Moon” and is the traditional Maori way of telling time. The new year begins with the first new moon following the appearance of the Pleiades (Matariki) on the horizon, in June or July.

Nepali calendar (sambat)

Its origin dates back to the year 2022 BC. On October 25, 2011, the government decided to put Nepal Sambat into use as the country’s national calendar, and created a group to give recommendations on its implementation.

yoruba calendar

It is used by the Yoruba people of southwestern, central, and northern Nigeria and southern Benin. The year begins with the last Moon of May or the first Moon of June of the Gregorian calendar. The traditional Yoruba week has four days.

biodynamic calendar

It is the evolution of the traditional lunarios used by farmers. The biodynamic calendar takes into account the phase of the Moon in relation to the visible constellations and is used in modern biodynamic agriculture to determine the best times to cut wood, plant, harvest or do other agricultural work. It is also used to choose the best day to cut your hair or wax.