What is perihelion and aphelion of earth?
In the solar system, perihelion and and aphelion are the positions of a solar orbiter (planet or comet or asteroid) when the the distance from the Sun is least and greatest respectively.
Also, they are used to give least and greatest distances. As the orbits are elliptical, by symmetry, the time for moving from either to the other is (orbit period)/2. For the Earth, perihelion is 1.471 E+08 km and aphelion is 1..521 E+08 km, nearly. The Earth reaches these positions in the first week of Jan and Jul.