EARLY SUNRISE and SUNSET : At sun Rise : When the Sun is just below the horizon , the light from the Sun suffers refraction from RARE to DENSER medium (As atmosphere is warmer than layers near the earth at that time) bends towards the normal at each refraction. Due to continuous bending of light rays, the Sun can be seen even when its actual positions just below the Horizon . As a result the Sun is seen in advance , two minutes before it rises above the horizon in the morning .
Similarly , in the evening Sun is seen delayed by $$2$$ minutes longer above the horizon after the Sun set.