# One timer per person Two items, each with its own stopwatch. Starting the second stops the first and saves its entry: the host's `onStart` hook stops whichever tracker runs and answers true, which is the one-running-timer rule of a time-tracking column. A hook may also veto (return `false`) or take time (return a promise): the button is held and the tracker is `aria-busy` until it settles. `start()` and `stop()` are public and say whether they did anything.