Biorhythm, derived from the Greek words BIOS 'life' and RYTHMOS 'regular', the clear ups and downs flows of life’s energy. We found 3 different curves. A physical cycle of 23 days long, an emotional cycle of 28 days, and an intellectual cycle lasting 33 days. Each period begins on the day someone is born. Half of each cycle is in a period full of positive energy and vitality, the other half in a negative or recovery period. The intersections with the zero line are the critical days who needs extra attention. On the physical level we will have more days of illness or extra tiredness. On the emotional level we are moody and downcast. And on the intellectual level we have difficulty to concentrate, not a good day to take an exam or a job interview.