This research is based on an executive resource theory of timing, which postulates that time perception relies on specialized attentional resources that support executive cognitive functions. In 4 experiments, older and younger participants performed a timing task and an executive task emphasizing inhibitory control under both single-task and dual-task conditions. The timing task in each experiment was serial temporal production. The executive tasks, representing different types of inhibitory control, were the flanker task (Experiment 1), the number-letter task (Experiment 2), the go/no-go task (Experiment 3), and the antisaccade task (Experiment 4). The results showed (a) a pattern of bidirectional interference in each experiment, in that the concurrent inhibition tasks interfered with timing performance and concurrent timing interfered with inhibition performance, (b) the older participants demonstrated a stronger bidirectional interference effect relative to younger participants in 3 experiments, and (c) weaker versions of the inhibition tasks produced weaker interference effects. These findings support the idea that temporal processing relies on executive attentional resources.