If a pendulum clock is accurate at sea level, will it gain or lose time when taken to high altitude? Why?

A pendulum clock works using gravity. Gravity pulls the m towards the equilibrium position at the bottom. Suppose your high altitude results in gravity being 1/10 what it was at sea level. Using F=ma, we see that the force due to gravity is smaller, m is constant, so acceleration must decrease. Since the pendulum cannot accelerate as quickly, it cannot reach the maxima on either side of the equilibrium as quickly, resulting in a loss of time. (The clock runs slower)