You know, the fact this was a trick question highlights a glaring flaw in T/SQL (or perhaps SQL in general?). Using single quotes for both strings and dates is a brain-dead design decision--period.
Would it be so hard to introduce a new quote character for dates, ala Access?
#02/21/2008# or #12/31/1899 14:23#
Ambiguity is a nasty design flaw, SQL Server (or SQL in general?) is far enough down the road this should have been fixed by now...