There is an absurdity saying that there are three days that shine more than anything a year. I prefer to say that there are two stars that are seen at sunset and dusk always: Venus and Mercury.
While the first is an invention without any basis, the latter is demonstrably true.
At sunrise or sunset, because the rays of sunlight are “parallel” to the ground, two stars, near and close to the sun, reflect the light of this and are brighter than the rest of the sky. Moreover, as these are virtually the horizon line, it helps your rays entering angle greater than the Sun and therefore do more with our eyes than the sun itself. Something like to leave at hours when the sun is highest gives more light and heat than the rest of the day because the rays are perpendicular to the ground completely. For here, the reflected rays of Venus and Mercury are more perpendicular than the rest. Simple. Physics explains everything.