> This is exactly the problem that prompted my other post on 
> xs:date.  I 
> can't use either xs:gYear or xs;date because some dates are 
> in the form 
> YYYY and some are YYYY-MM, and still others YYYY-MM-DD.  So, I had to 
> change to substring(.,1,4) to get the stylesheet to compile.
> 
> I really wish xs:date would count all of these as valid.

You can of course define a union type my:anyDate in your schema with
xs:date, xs:gYear, and xs:gYearMonth as its member types, and with a
schema-aware XSLT processor you can then refer to the type my:anyDate in
variable definitions and function signatures. You can use the "instance of"
operator to test which of the different kinds of date the value actually
holds.

Michael Kay