Really interesting subject Scrap. Circadian rhythms - the ones on a daily cycle - are the easiest to pick up on. Brain wave and hormone activity go up and down throughout the day effecting things like concentration and alertness. I think there are meant to be even shorter ones too. The longer ones are said to span over weeks, months and years.

I'm not sure if the longer rhythms actually exist. Far too difficult to measure accurately. Predicting someone's rhythms in say 2 months time on a given day with all the other variables involved would be hit or miss. We all know instinctively that things often go in cycles. But are these cycles regular?

Sounds like a good theory but I think there's an element of randomness to individuals biorhythms and so wouldn't stand up scientific scrutiny.

But if it works for you .......