Biorhythms
Three waves that start on the day you were born: one of 23 days, another of 28 and another of 33. It is a curiosity from the early 20th century; here you only see the wave.
Important: biorhythms have no demonstrated scientific basis. They cannot tell you how you will feel, how you will perform or anything about your health: take it as a game of numbers.
We do not store the dates: they are calculated on the spot and not recorded.