This problem pertains to an ADO datasource accessed via the following URL:
sdbc:ado:Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Program Files\Common 
Files\ODBC\Data Sources\FINANCE.mdb;Mode=Share Deny None;Persist Security 
Info=False

Suppose you have a table like this:
CREATE TABLE CHECKS
    ("RECID"            INTEGER         PRIMARY KEY,
     "POSTEDDATE"       DATETIME        NOT NULL,
     "PAYEE"            VARCHAR(40)     NOT NULL,
     "BANKTRACE"        INTEGER         DEFAULT NULL,
     "TRANDATE"         DATETIME        DEFAULT NULL,
     "VENDTRACE"        INTEGER         DEFAULT NULL,
     "AMOUNT"           MONEY           NOT NULL,
     "MEMO"             VARCHAR(40)     DEFAULT NULL  )

In the Query Designer make a query that results in the following SQL:
SELECT `POSTEDDATE`, `PAYEE`, `BANKTRACE`, `TRANDATE`, `VENDTRACE`, `AMOUNT`, 
`MEMO` FROM `CHECKS` `CHECKS` WHERE ( ( `POSTEDDATE` >= {D '2003-07-01' } AND 
`POSTEDDATE` <= {D '2003-07-31' } ) ) ORDER BY `POSTEDDATE` ASC

That produces correct results.

Now, change it to a prompted query like this:
SELECT `POSTEDDATE`, `PAYEE`, `BANKTRACE`, `TRANDATE`, `VENDTRACE`, `AMOUNT`, 
`MEMO` FROM `CHECKS` `CHECKS` WHERE ( ( `POSTEDDATE` >= :sDate AND 
`POSTEDDATE` <= :eDate )) ORDER BY `POSTEDDATE` ASC

Respond to the prompt with 7/1/03 and 7/31/03. (I'm in USA so that's M/D/YY)
Now, the result is only 2 rows with with POSTEDDATE of 7/31/03.

Note also that a response in the form YYYY-MM-DD is not accepted. I think
that too is a bug.

Also note that that Query Designer will not accept the more obvious
BETWEEN date1 AND date2. Also a bug.