looking for story of Hermione as an old lady

[mrs_sonofgib]

Hi all!  It's been a while (cough, cough) since I've posted but I've
been lurking.  I remember reading a short story (kind of) of Hermione
as an old lady.  It was explaining how wizards age vs. us muggles.  In
the story she was spritely and would ride by on her bike and wave at
her neighbor who is aging normally.  I don't remember the rest of the
details.  Does anyone remember this and can you direct me to it?  Any
and all help will be greatly appreciated!
Thanks,
Tina