When I first met folks in Las Vegas that used biorhythm values of the top players in a team to place their bet, I thought they were a little odd. Some of them were successful, but I am sure biorhythms were not the only thing they considered. You can read more about biorhythms at:
http://en.wikipedia.org/wiki/Biorhythm
This snippet shows a simple Python code to calculate the three standard biorhythm values centered around the present day, based on the your age in days. To expand the program you can use VPython to plot the values, let's say for the period of a month. See:
http://www.daniweb.com/code/snippet376.html