It can vary from year to year, but is always within about a day either side of January 3rd .
The Earth reaches perihelion (point closest to the Sun) around January 3rd.
In January
It is closet on Janurary 4th or around Janurary 4.
The Earth is closest to the sun in the summer for the southern hemisphere and winter for the northern hemisphere due to it's elliptical orbit. Perihelion (Earth's closest approach to the sun) happens...