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]