It has come full circle, as a seasonal cycle might be expected to do.

This revealed that the seasonal cycle of flu epidemics mirrored the humidity of the air, and a drop in humidity led to outbreaks of flu.

The same seasonal cycle has been recorded every year since then.

After 3,300 years even this calendar will diverge a whole day from our seasonal cycle.

They lived a semi-nomadic life that followed a seasonal cycle.