Because the Earth orbits the Sun, by the time it completes one >revolution, the location on the earth closest to the sun has shifted a bit.
(the Earth; orbits; the Sun) (it; completes; one >revolution; T:the time) (the location on the earth closest to the sun; has shifted; a bit; T:by the time)
the Earth it the location on the earth closest to the sun
orbits completes has shifted
the Sun
one >revolution T:the time
a bit T:by the time