parsing dates

[James Cummings]

Hi there,

I've a silly question about the best way to parse dates.  I'm passing
a parameter (in eXist) that is part of the URL for an xquery and I
want to separate it into its individual parts of year month and day. I
could test the string and do substring-before and after and such, or
create my own function, but it seemed better practice to use the
functions like year-from-date and month-from-date.  So I tried:

let $date := request:get-parameter("date", ("1789-01-01")) cast as xs:date
let $year := fn:year-from-date($date)
let $month := fn:month-from-date($date)
let $day := fn:day-from-date($date)

which works fine when the date is YYYY-MM-DD.  But what I want to
achieve is being able to handle YYYY-MM-DD, YYYY-MM or just YYYY.  The
last two give me an error of "xs:date must not have hour, minute or
second fields set" (erm... which it doesn't, which is why I'm
confused). I'm happy for $month and $day to be empty if they don't
exist.

I'm sure it is something terribly obvious with the datatype.  Should I
just be breaking it down to its component parts myself?  It just
seemed like I was reinventing the wheel.

Thanks for any suggestions.

-James