Why is there no 30 in May in the lunar calendar?
The lunar calendar is a traditional Chinese calendar, which is different from the Gregorian calendar (Gregorian calendar) in that its month length and leap month rules are more complicated. When many people look at the calendar, they will find that the fifth month of the lunar calendar often does not have 30 days. Behind this phenomenon lies the unique logic of the lunar calendar. This article will combine the hot topics and hot content of the past 10 days, analyze the reasons why the lunar calendar lacks 30 days in May, and display the relevant background through structured data.
1. Basic rules of lunar months
The lunar months are based on the lunar cycle (the synodic moon) and have an average length of 29.53 days. Therefore, the lunar months are divided intoSatsuki (29 days)andBig month (30 days), the specific allocation needs to be adjusted based on actual astronomical observations. The following is the statistics of the number of days in the lunar month of May in the past 10 years:
| Year | Number of days in May on the lunar calendar |
|---|---|
| 2023 | 29 days |
| 2022 | 29 days |
| 2021 | 30 days |
| 2020 | 29 days |
| 2019 | 29 days |
2. The reason why there are no 30 days in the fifth month of the lunar calendar
1.Moon phase cycle restrictions: The synodic month cycle of May in the lunar calendar is usually less than 30 days, resulting in May being a small month in most years.
2.Adjustment of solar terms: The lunar calendar needs to be coordinated with the 24 solar terms. If May includes the summer solstice (around June 21 in the Gregorian calendar), its length is more likely to be compressed.
3.Historical observation data: According to calculations by the Purple Mountain Observatory, the fifth month of the lunar calendar lasts 29 days in 60% of years.
3. Related topics of recent hot topics
In the past 10 days, discussions about the lunar calendar have beenDragon Boat Festival (the fifth day of the fifth lunar month)It heats up as it approaches. The following is a social media popularity analysis:
| topic | Number of discussions (10,000) | Related points |
|---|---|---|
| Dragon Boat Festival holiday arrangements | 125.6 | Correspondence between lunar calendar dates and Gregorian calendar |
| Popular Science on Lunar Calendar Algorithm | 87.3 | Causes of formation of big and small moons |
| Summer Solstice Customs | 42.1 | The relationship between solar terms and the lunar calendar |
4. Comparison of the differences between the lunar calendar and the Gregorian calendar
The following table shows the key differences between the lunar and Gregorian calendars, further explaining the absence of 30 days in May:
| Comparative item | lunar calendar | Gregorian calendar |
|---|---|---|
| Baseline | moon phase cycle | earth revolution period |
| month length | 29 or 30 days | 28-31 days |
| Leap month rules | 7 leap years in 2019 | 1 leap in 4 years |
5. Interpretation from cultural perspective
In traditional Chinese culture, the fifth lunar month is regarded as"Poison Moon", the ancients believed that Yang Qi was extremely strong at this time and should be avoided. This cultural perception may have influenced the calendar arrangement, favoring shorter days in May. Recently hotly discussed on the InternetPlanting mugwort at Dragon Boat FestivalThe custom is also closely related to the particularity of the fifth month of the lunar calendar.
Conclusion
The lack of 30 days in the fifth month of the lunar calendar is essentially the result of the interaction between astronomical laws and cultural traditions. With the arrival of the Dragon Boat Festival, this topic will continue to arouse public attention to the traditional calendar. Understanding the logic of the lunar calendar not only satisfies intellectual curiosity, but also helps to better inherit the wisdom of Chinese culture.
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