IB ss 6 / IBO 3.6 Ca / D4

I use the data format string ddddd which reflects users choice of any
given short date format.
In the on prepare event of a stored procedure, query or cursor I provide

SQLWhereItems as date and others.

Only dmy, mdy, ymd works for stored procedures, and worse only mdy, ymd
works for queries and cursors. That's no good. The user should be able
to pick any format they want!

This looks to me as though there is some filtering being done here
implying restrictions as to what date format the user can select unless
the application performs an expensive date format analysis to provide in

turn the restricted date format for queries.

What's wrong here?
Who is it?
Interbase or IBO?
Am I missing something?

Cheers

Johannes