Critical days
The daythe lineis crossed.
A critical day is when a cycle passes through its midline and turns. A moment of change, read as a pause, never as a warning.
01 · The crossing
Every lap meets the midline three times.
Once on day 1 as the cycle rises, and twice about half way through as it falls. Between states, the theory says, a little less settled than usual.
Physical
A 23-day lap
1rising · c
12 & 13falling · C
Emotional
A 28-day lap
1rising · c
15 & 16falling · C
Intellectual
A 33-day lap
1rising · c
17 & 18falling · C
3
critical days in every lap. The app marks the rising one with a small c and the falling pair with a capital C. The fall takes two whole days to pass through the line.
02 · When they line up
Sometimes two cross together. Rarely, all three.
Because the laps are different lengths, their crossings drift apart and only occasionally meet. The theory calls these double and triple critical days.
12
double days a year
Two cycles on the line on the same day.
26
triple days in 58 years
All three at once, after the birthday. Popular writing in the 1970s made a great deal of them.
03 · How to read one
A prompt, not a warning.
A critical day in the app looks like any other day with one of its symbols changed; the written reading for the day takes account of it. There is nothing to avoid and nothing to do. If a critical day is useful at all, it is as a reason to notice how you feel and to ask whether the pattern fits. Sometimes it will seem to; often it will not. Either answer is fine.
BioCalendar does not say that critical days are dangerous, that accidents or illness are more likely on them, or that decisions should be put off. Those claims were made in the 1970s, they were tested, and they did not hold up.
04 · What the evidence says
The most tested claim. It did not hold.
Accidents are easy to count, so in the 1970s researchers compared their dates with the critical days of the people involved.
- 01
Industrial accidents
No clustering on critical days
- 02
Traffic accidents
No clustering on critical days
- 03
Aviation accidents
No clustering on critical days
Keep reading
- What is a biorhythm?A biorhythm is a cycle said to begin at birth and repeat on a fixed period: 23 days physical, 28 emotional, 33 intellectual. The theory and the evidence.
- How to read a biorhythm chartThe three cycles, the eight states each passes through, the symbols BioCalendar uses for them, and what a critical day, a high and a low mean on the chart.
- Are biorhythms real?What the studies found when they tested biorhythm theory against accidents, sport, exams and deaths, why people use it anyway, and how we frame it.