No, this does not mean that 82.5% of a year has elapsed - think about
it: it is now March and the reference date was in January of last year,
so more than one year has elapsed. Alternatively, the reference date
was 1st October, so we are now about half a year past that date (I
don't know if you are working with mm/dd/yy or dd/mm/yy format dates).

You need to put a date in cell H13 for it to work correctly. If you
make it 20/03/2006, then you should get 1.189041, and you need to
format this cell as percentage with no decimal places if you want it to
show 119%. To follow the alternative date format, enter 03/20/2005 and
you will get 47%.

If you want to avoid spurious values, then change the formula to this:

=IF(H13=0,"",(H13-DATEVALUE("10/01/2005"))/365)

This will give you a blank result if there is nothing in cell H13.

Hope this helps.

Pete