Group 1 - The article discusses the occurrence of a leap month in the lunar calendar, specifically the leap sixth month, which will not happen again until 2036 [1][4] - The leap sixth month started on July 25 and ended on August 22, lasting 29 days, which is classified as a small month [1][4] - The leap month phenomenon occurs every 2 to 3 years, with the next leap month expected in 2028, which will be a leap fifth month [4] Group 2 - August 23 marks the beginning of the lunar seventh month and coincides with the solar term of Chushu, which is significant in the agricultural calendar [6] - The lunar seventh month includes the traditional Chinese festival of Qixi, which falls on August 29 this year, delayed by 19 days compared to last year due to the leap month [6]

Core Viewpoint - The article discusses the traditional Chinese lunar calendar, its structure, and the phenomenon of leap months, emphasizing that leap months are a normal occurrence in the calendar system and not related to climate anomalies [1][10]. Group 1: Lunar Calendar Structure - The lunar calendar is based on the moon's orbit around the Earth and the Earth's orbit around the sun, making it a lunisolar calendar [1]. - A lunar month is determined by the lunar cycle, averaging 29.53 days, leading to a lunar year of approximately 354 or 355 days, which is about 11 days shorter than a solar year [5]. - To align the lunar calendar with the seasons, ancient astronomers implemented a leap month system, adding 7 leap months in a 19-year cycle [6]. Group 2: Leap Month Mechanism - The leap month is determined based on the presence of solar terms, which divide the Earth's orbit into 24 segments, ensuring that each lunar month contains a solar term [6]. - If a lunar month lacks a solar term, it is designated as a leap month, with the current example being "leap June" in 2023, which has 29 days [7]. Group 3: Historical Context and Climate Relation - Leap June occurrences are not rare, with six instances recorded in the current century, including years like 2017 and 2025 [10]. - Recent extreme heat has been mistakenly linked to the leap month phenomenon, but experts clarify that leap months are a standard calendrical occurrence and do not indicate climate anomalies [10].

Core Viewpoint - The article discusses the occurrence of a leap month in the lunar calendar, specifically the leap June in 2023, and explains the astronomical reasoning behind it [2][6]. Summary by Sections Lunar Calendar Explanation - The lunar calendar is based on the moon's orbit around the Earth and the Earth's orbit around the sun, making it a lunisolar calendar [2][6]. - A lunar month is approximately 29.53 days, leading to a lunar year of about 354 or 355 days, which is about 11 days shorter than a solar year of 365.24 days [6]. Leap Month Mechanism - To align the lunar calendar with the solar calendar, ancient astronomers introduced leap months, adding 7 leap months in a 19-year cycle [6]. - The placement of leap months is determined by the 24 solar terms, which divide the Earth's orbit into 24 segments [6]. Current Leap Month Details - In 2023, the leap month is designated as "leap June," occurring from July 25 to August 22, with only one solar term (Liqiu) present in this period [6]. - The leap month has 29 days, and the absence of a solar term in the preceding month led to its designation as a leap month [6]. Frequency of Leap Months - This century will see a total of six occurrences of leap June, specifically in the years 2017, 2025, 2036, 2055, 2074, and 2093 [7]. Climate Connection - The article clarifies that the recent extreme heat is not related to the leap month phenomenon, emphasizing that leap months are normal occurrences in the lunar calendar [8].