What does double happiness mean?

It means that the two festivals are very close, only a few days apart. When blessing others, it can be said that both festivals are happy. The situation of two festivals often appears in daily life.

For example, the Mid-Autumn Festival on 20 15 and 20 17 are very close to the National Day, and the National Day and Mid-Autumn Festival in 2020 coincide on June 65438+ 10/.

The reunion of Mid-Autumn Festival and National Day is mainly due to the leap month. Astronomical experts say that this situation is mainly the result of leap month. According to the director of Tianjin Astronomical Society, the Chinese lunar calendar stipulates that there are 30 days for the big moon and 29 days for the small moon, and a year is 12 months * * 354 or 355 days, which is about 1 1 day less than a tropical year. It will be less than 1 month in four years.

Non-leap month:

(1) Leap May is the most common leap month among all leap months, and leap April and June are also common leap months.

(2) The frequency of leap July is second only to leap April, leap May and leap June, so it is called the more common leap month.

(3) The frequency of leap months in February, March and August is second only to that in July, so these three leap months can be called intermediate frequency leap months.

(4) The frequency of leap September and October is second only to leap February, March and August, and the years of leap September and October are relatively few, so these two leap months can be called rare leap months.