Left: rates of period change computed from stellar evolution tracks assuming moderate convective core overshoot, α_c = 0.2 and initial rotation rates of 0,100,200, and 400 km s^-1. Right: rates of period change computed from stellar evolution tracks assuming zero rotation and convective core overshoot, α_c = 0,0.2, and 0.4. The different colors are the same as for Fig. 1 while the horizontal orange line denotes the measured rates of period change for ξ¹ CMa and δ Cet and the gold line denotes the second measured value for δ Cet.