If anyone remembers Biorhythms, here is a Macro to make a Biorhythm chart.
There is an option on line 48 of the macro to chart 90 days instead of one month.
If you chart 2 months after your 58th birthday you can see the sine waves starts over.
If you type in 2 digits for the year (i.e. 57) it adds 1900 for the year (i.e. 1957).