I asked this question a while ago but no one seemed to be able
to provide a definite answer. I've looked through everything I
own and everything I can get my hands on and I haven't been
and to find anything that answers my question absolutely.

So...How do we know that Asuka is born in 2001?

That is, how do we know that her birthday is the 4th of
December 2001. Which would make her 13 when the series
starts. Everyone seems to assume she was born in 2001, I
do too, but I haven't been able to find anything to back it up.

We know she was born on December 4th (same as Miyamura
Yuuko's birthday) but I have never been able to find any official
information on the year of her birth. If anyone could help I would
really appreciate it.

--
Michael Wignall