How did the ancients know the calendar of the day? For example, modern people don't know the calendar, so they look at their mobile phones. When I was a child in primary school, I let it grow.

Every year, the official will print the yellow calendar, and ordinary people can't print it privately. In addition to dates, solar terms, good and bad luck of each day, dry branches, stars and moons will also be recorded on the yellow calendar. Even the time of farming and mulberry will be marked, and the people will live and work with reference to the yellow calendar. What we use most now is the Gregorian calendar, which is based on the direction of the sun, only indicating time, and there is no taboo or anything.