Biorhythms draw three waves calculated from birth. Physical, emotional and intellectual are names of cycles in the model, not personal measurements. Explore how their periods create alignments and crossings while distinguishing the chart from how you actually feel.

Count whole calendar days and calculate sine(2π × days / period). Chart and values use −100 to +100; bars place that value between the two extremes. The center is the selected date, with 15 days on either side.

From 28 February 2000 to 1 March, two calendar days have passed: that year included 29 February. The model gives about +52, +43 and +37 out of 100 for its 23-, 28- and 33-day cycles. These values locate points on waves, not percentages of personal ability.