What six days can't the fairy stay to see the patient?

Six-day fast: the eighth, fourteenth, fifteenth, twenty-third, twenty-ninth and thirtieth day of each month (abortion is changed to twenty-eight, that is, abortion is the eighth, fourteenth, fifteenth, twenty-third, twenty-eighth and twenty-ninth).

Note: It is the lunar calendar.

As for why, I don't know, mainly because the fasting period is supposed to be "clean" and the patients are "filthy" according to Xuandao. Of course, in modern society, don't be too superstitious ...