As we know that time period of simple pendulum will be

now we will have
time period of a clock on the surface of earth will be 1 s where we have acceleration due to gravity is g = 9.8 m/s/s
now if we took the pendulum to the surface of moon where acceleration due to gravity will be 1.65 m/s/s then this time period will change
so we will say by above equation

now we will have

now plug in all data in this


so time period on moon will be 2.44 s