Is there really a scientific basis for auspicious days? Is it accurate?

Well-founded, but not entirely accurate. Take the most common example:

Girls come to menstruation, feel uncomfortable, and have poor work and study efficiency, which can be said to be "everything is not suitable". This is a "bad day".

This day can be predicted, and every girl will make her own prediction. Its essence is caused by the change of the distance between the moon and the earth. Different distances produce different gravitational forces, which leads to different menstrual periods for girls.

By extension, the good or bad luck of the zodiac in China and the astrological fortune of foreigners are all related to the arrangement and combination of the position relationship between the stars running to a certain point and the earth. If it is based on science, it can only be explained this way. But not necessarily, because there are many factors, some of which are unpredictable. For example, a girl had her period one day and felt unwell, but when she won the lottery that day, her discomfort would be forgotten.