While the strong anticorrelation between chromospheric activity and age has led to the common use of the CaII H and K emission index (R'_HK_=L_HK_/L_bol_) as an empirical age estimator for solar-type dwarfs, existing activity-age relations produce implausible ages at both high and low activity levels. We have compiled R'_HK_, data from the literature for young stellar clusters, richly populating for the first time the young end of the activity-age relation. Combining the cluster activity data with modern cluster age estimates and analyzing the color dependence of the chromospheric activity age index, we derive an improved activity-age calibration for F7-K2 dwarfs (0.5<B-V<0.9mag). We also present a more fundamentally motivated activity-age calibration that relies on conversion of R'_HK_ values through the Rossby number to rotation periods and then makes use of improved gyrochronology relations.