<http://schema.org/about>
"Jan. 2 marks the time when the Earth is at perihelion, the point in its orbit at which it is closest to the sun."^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.mnn.com/earth-matters/space/stories/earth-is-closest-to-the-sun-for-2013-today>