Relations between the observed rotational and cycle periods, and versus age. Stars with simple cycles are plotted with red dots, stars with complex cycles with blue squares, and the Sun with an orange star. The components of the wide binaries HD 131156A/B and HD 201091/HD 201092 are connected. Top: P_cyc/P_rot show a clear separation between stars with simple and complex cycles in the sense that the simple cycles have about the same value, while complex cycles are more scattered. The division occurs near the age of the Vaughan-Preston gap (Donahue 1996). Middle: average of the stars from Barnes (2007); the younger stars, especially below 1.5 Gyr, have a higher average activity. Bottom: P_rot of the stars as a function of age, showing a clear separation, also near the Vaughan-Preston gap. The range of the rotational periods in NGC 6819 and M67 at their ages of 2.5 Gyr and 4.2 Gyr are shown by green lines; data taken from Meibom et al. (2015) and Barnes et al. (2016).