Let
The clock is an absolutely continuous function and is strictly increasing: its derivative is positive away from the Brownian zero set, which has zero Lebesgue measure. It also tends to infinity. This is immediate for ; for , recurrence and the Strong Markov property imply that the Brownian occupation time of, for example, is unbounded, while the integrand is bounded below there by .
Thus is continuous, strictly increasing, and maps onto itself. Its inverse function is finite, continuous, and strictly increasing.