Twenty-eight.
1. Twenty means twenty, so twenty-eight is twenty-eight. Lunar twenty is written as twenty (read: nian) in the lunar calendar. For example, twenty-one is twenty-one, twenty-two is twenty-two...
2. The character twenty is caused by the development of calligraphy. One horizontal and one vertical is ten, one horizontal and two vertical is twenty, and later the lower parts were connected, which is called nian. One horizontal and three vertical is thirty, pronounced thirty (sa), one horizontal and four vertical is forty, pronounced 卌(xi).
3. Twenty comes from the Chinese lunar calendar. The lunar calendar is our country’s traditional calendar and has names such as the lunar calendar, the Chinese calendar, the summer calendar, the Chinese calendar, and the Chinese calendar. The lunar calendar is not a pure lunar calendar, but a combined lunisolar calendar. The length of the month is added to the "twenty-four solar terms" of the stem and branch calendar. The length of the year is based on the solar return year. Leap months are set to make the average calendar year adapt to the return year. The lunar calendar is also a calendar that takes into account the relationship between the sun, moon and earth. The lunar calendar does not take into account the movement of the earth around the sun, so the changes in the four seasons have no fixed time on the lunar calendar and cannot reflect the seasons.