Let's say they counted a year as
exactly the time the earth needs to revolve around the sun
then the explaination with the
Since we don't have any clue in what time this story plays we could assume
That Sue and Thomas are people living in the future (2217 or so).
an astronaut travelling at a very high speed (> 0.1c)
travels back to earth,
time on earth has actually gone faster (so that Thomas may be 2 days older)
(because of special relativity, see below)
but they lived the exactly same amount of
This effect is called
and can actually be measured with today's technology.
Why is Thomas older and not Sue?
Sorry that I'm not using some of the provided numbers, but I really wanted to bring this kind of lateral-thinking in.