The SQL 92 spec is quite specific that there is an exact order for date
and it is yyyymmdd period, and that these are constrained by the rules of
a well formed gregorian calendar (i.e. no 20020231 allowed)
Seeing as how putting in 2002-22-04 and 2002-04-22 on my box results in
two inputs of april 22nd 2002, it's obvioue postgresql is trying to make
data fit that should result in a constraint violation.
I found this on p 110-112 or so of the SQL92 draft in text that's so
common. it's section 6.1 or so.