During a sunset, mountain peaks lose sunlight later than areas around them. From a viewer observing a mountain, a shadow can appear ascending from the base to the peak. And conversely, during a sunrise, mountain peaks get sunlight before the areas around them and a shadow can appear descending from the peak to the base.
This phenomenon occurs because the Earth is a sphere. As the altitude increases, the hours of daylight become longer. It makes the sun rise earlier and set later.
With an elevation of 8,848 Meters (29,029 feet), sunset would be about 15 minutes later on the peak of Mount Everest than on sea level. And similarly, sunrise would be about 15 minutes earlier than on sea level.
This phenomenon can never be explained in the flat Earth model. On the other hand, in the spherical Earth model, not only it can be explained, but the occurrence can also be calculated, and the result will be 100% consistent with observation.
Videos of Sunsets at Mount Everest