24 hours a day, that is 1440 minutes. A normal clock, counting from 0 o'clock, overlaps 22 times a day, regardless of seconds. The average time of each overlap is (1440/22) minutes, that is to say, this old clock is slower than the normal clock every time.

66-( 1440/22) minutes, so a day is 22 * (66-(1440/22)) =12 minutes. (22 times can be studied or counted by yourself)