Dates are tricky because there's no good date class in Java that supports,
timezone, time, dates, etc separately.
This is necessary because XML Schema Part 2 defines a whole series of
builtin types
like gYearMonth and gMonthDay.
Current design allows me to output XML using sclaxb.toXML for both
schema-originated
types and built-in types. If I made everything into some kind of
Calendar/DateTime class,
it won't be able to round trip back to XML.
scalaxb.toXML[Calendar](x, None, Some("foo"), defaultScope); //
dateTime, gYearMonth, etc?
XMLGregorianCalendar is nice because the capability is built into the class.
-eugene