How did the ancients know that a year is about 365 days with a standard watch?

Just make a disk, scrap the disk, and scale it outward from the center of the circle, 360 degrees will do. Place a steel needle vertically at the center of the circle on the fixed platform, and the position cannot be moved. Every day when the sun comes out, observe the scale on which the shadow of the hour hand falls on the disk, and make a record. Of course, the data of the last sunshine in weighing scale should also be recorded, so that you will find that the data is different every day, that is, the length of a day (daytime) is different. After about 365 days, the same data as in the past will be recorded, which means that one year has passed.

Note: The larger the dial, the longer and thinner the steel needle, and the more accurate the data. Raining on cloudy days can be regarded as reference data. The higher the ground, the more accurate the position. In the city, the top floor of more than ten floors is the best.