September 28 is an ordinary day in Japan, but in Taiwan, it is Teacher’s Day, called 教師節 (Jiàoshī jié) in Chinese.
This is because it corresponds to the current September 28 when converted from the lunar calendar for the birth of the sage Confucius, a thinker from China’s Spring and Autumn Period and the founder of Confucianism, and was established based on the significance of expressing gratitude to teachers.

Teacher’s Day is called the Festival of Teachers, but that does not mean teachers get to take the day off.
However, on this day, students give their teachers presents and flowers, write letters, and express their appreciation in various ways.
Since it is Confucius’s birthday, on September 28, a grand ceremony is held at Confucius Temples to honor Confucius. (A Confucius Temple is a mausoleum enshrining Confucius.)
By the way, China’s Teacher’s Day is September 10, at the start of the autumn semester.