This patch fixes a nasty little bug that shows up when #xmlschema is called on a Date/DateTime that's out of range of the Time class (~1902-2038) -- you either get this exception:
SystemStackError: stack level too deep
or a fatal error, which brings down Mongrel or script/console, with this message:
Illegal instruction
The fix is simple -- I've added a DateTime#xmlschema method, so that Date#xmlschema doesn't get stuck in an endless loop of trying to convert a Date to a Time.