Because of Earth's elliptical orbit, the planet varies its distance from the Sun.

(From http://science.msfc.nasa.gov/headlin...ast04jan_1.htm)
"perihelion both hemispheres were 147.5 million km from the Sun."
"152.6 million km in July, which astronomers call aphelion"
A difference of 5.1 million km.

the speed of light = 299 792 458 m / s

(5100000000 m)/(299792458 m/s)=17.01 seconds

How much variance would this introduce in the EoT? Would this
difference add up to an appreciable amount?
--
CB