There is a fundamental flaw with the usual biorhythm approach, namely the assertion that biological clocks such as those governing the cyclical variations in our physical, emotional, and intellectual well-being keep ticking with absolute accuracy and stability over decades. This is difficult to believe even for non-scientists. A 1% percent uncertainty in the stability of these clocks would result into drastically different patterns by the time one reaches adulthood.
But there is nothing wrong with expecting periodic, more or less regular, ups and down in the way we feel and perform.
There is a way to eliminate this flaw. Instead of relying on one's time of birth and an unrealistic reliability of one's biological clocks one can directly determine where one happens to be RIGHT NOW on each one of the three cyclical curves via a sophisticated method leveraging the sensitivity ingrained in the second mathematical derivative.
This method is described in my book "Street Science" and has been cast in a software application.
The interested reader can look it up.
Theodore Modis, Ph.D.
Growth Dynamics