In the lunar calendar, a leap month is a special addition that not only reflects the wisdom of ancient Chinese calendrical systems but also relates closely to our daily lives. The leap sixth month of 2017 is a typical example. This article will guide you to understand what the leap sixth month is and the underlying calendrical principles.
Definition and Origin of the Leap Month
A leap month in the lunar calendar is an additional month added to compensate for the time difference between the solar year and the lunar year. Since the lunar calendar defines large months as 30 days and small months as 29 days, a year of 12 months totals 354 or 355 days, which is about 11 days less than a tropical year. Therefore, approximately every three years, an extra month must be added to maintain the accuracy of the calendar. This adjustment method is known as "seven leap months in nineteen years," meaning that one month must be added every two to three years.
How to Determine the Leap Month
The rules for determining the leap month are related to the winter solstice. In the Chinese lunar calendar, the month containing the winter solstice must be the eleventh month. Additionally, if between one winter solstice and the next, excluding the respective winter solstice months, there are only 11 full months, no leap month is needed. However, if there are 12 full months, a leap month must be inserted between the two winter solstices.
Arrangement of the Leap Month
In ancient calendrical systems, there are 24 solar terms, divided into "solar terms" (jie qi) and "mid-term" (zhong qi). Since the average length of two solar terms in the Gregorian calendar is about 30.5 days, while a lunar month is only 29.5 days, it inevitably results in a month that has only a solar term but no mid-term. According to regulations, each lunar month must have both a solar term and a mid-term. Therefore, the month that only has a solar term and no mid-term is designated as the "leap month."
Reasons for the Leap Sixth Month in 2017
During the period from the winter solstice of 2016 to the winter solstice of 2017, excluding the respective winter solstice months, there were 12 full months. Therefore, a leap month was required. If no leap month was added, the winter solstice of 2017 would fall in December. According to the arrangement of the months in 2017, the leap sixth month was from July 23 to August 21. In this month, only the "End of Heat" (Liqiu) solar term on the 16th day of the sixth lunar month occurred, while the mid-term "Great Heat" (Chushu) fell on the second day of the following month. Therefore, this leap month was called the leap sixth month.
Leap Month and Seasonal Changes
Although the leap month adds an extra lunar month, it does not affect seasonal changes. The alternation of seasons is mainly due to the Earth's revolution around the Sun. A leap month has no direct connection with weather or seasonal changes, so there is no need to worry that summer will become longer.
Leap Month and Wedding Customs
In traditional customs, the leap month is considered auspicious, symbolizing the nourishment and harmony of love between couples. The leap sixth month, being a double month, is particularly considered a good time for marriage. The occurrence of a leap month is not random but determined by the Earth's revolution and calendrical rules.
The leap sixth month is a special month in the lunar calendar designed to adjust the time difference between the solar year and the lunar year. It not only reflects the scientific nature of ancient Chinese calendrical systems but is also closely related to our traditional festivals and customs. Understanding the origin and significance of the leap sixth month helps us better understand and inherit Chinese traditional culture.
