Question

If all the glaciers of earth will melt then what effect on earth rotation

Answer 1

Melting ice triggered by global warming may make Earth whirl faster than before and could shift the axis on which the planet spins.
This could also affect sunset times, as thelength of Earth's daydepends on the speed at which the planet rotates on its axis. 

Answer 2

this would affect the time of the sunset
this would make the earth whirl faster
and this would decrease the duration of day as day depends on the rotation. of the Earth