to indicate that the user does indeed intend to use an ISO date literal might be a slightly better idea. Then the compiler actually has something to grab and use the correct algorithm.
Overloading a literal indicator sounds like a coding nightmare. And since we see enough examples of people attempting to misuse the current date, datetime and time literals I'm not sure that I want spend more time explaining why date literals in all the other forms attempted aren't valid.
I really like the general idea of opening up the date and datetime literals to, at least, using the ISO formats. I wonder if it would be better to allow the literals to accept any of the values currently accepted by the ANYDTDTE or ANYDTDTM informats ?
I'd be happy to accept BallardW's idea of an expanded family of literals such as id or idt or even a broad-minded ad or adt to allow for a nice bit of backwards compatability.