There are no solar terms in leap months.

On the time scale longer than the sky but shorter than the year, the phase change of the moon is a convenient way to calibrate the time period. In ancient times without modern tools, it was a very simple calendar to directly determine the relative date by observing the moon. The traditional lunar calendar in China is based on the changes of the phases of the moon. In contrast to the Gregorian calendar, it is completely impossible to determine the size of the moon that night by date, which is very inconvenient in ancient times without street lamps: P

The root of the problem is that the moon phase period and the period of revolution of the Earth (in other words, we can say "solar phase period", just for comparison ~) are not integer multiples, so accumulated errors will occur. This needs to be adjusted according to leap month after a certain error occurs.

In fact, the lunar calendar is not equal to the lunar calendar. In order to meet the needs of farming, people added solar terms to the lunar calendar. The solar terms are determined according to the position of the ecliptic of the sun, which completely conforms to the solar calendar and is consistent with the Gregorian calendar in principle. In fact, I personally think that the solar terms run closer to the sun than the Gregorian calendar. It can be said that the lunar calendar+solar terms = lunar calendar is a typical lunar calendar.

On the other hand, the solar calendar itself has accumulated errors, most of which come from the relationship between the earth's rotation and period of revolution's non-integer multiples. Therefore, the Gregorian calendar also needs to be adjusted according to leap days. Of course, the Gregorian calendar stipulates that leap day occurs on the last day of February every four years, so this February is also called leap month, but this leap month is completely different from that of the lunar calendar. In addition, losing a leap day every 400 years is actually quite complicated.

The number of days in each month in the Gregorian calendar is not necessarily the same, and there is no law between large months and small months, but the number of days in each month is fixed and established. In addition, the setting of "week" is a multiple of 7, which has no integer multiple relationship with month and year. In history, it is even more bizarre and unreasonable, but it is just an agreement.

The lunar calendar itself is not unscientific, but also has its adaptation and practical side. Only today, people have a very convenient way to calibrate the time and calendar, and their work and life are based on the "week" of the Gregorian calendar, so it is more convenient for everyone to pass the Gregorian calendar. Except for the Lunar New Year holidays, people basically follow the Gregorian calendar in real life. In fact, the lunar calendar has been abolished. Did you make it more out of tradition?