Try giving this a go:

SELECT *
FROM JournalEntryDebitLine UNOPTIMIZED
WHERE (((JournalEntryDebitLine.TxnDate)>={d'2006-05-16'}))

See: How do I setup the QODBC Optimizer? Where are the Optimizer options? for more on this.

The QuickBooks sample files set the QuickBooks system date at Dec 15, 2007, so I have used these sample journal statements to test future dates:

INSERT INTO "JournalEntryCreditLine" ("TxnDate", "RefNumber",
"JournalCreditLineAccountRefListID", "JournalCreditLineAmount",
"JournalCreditLineMemo", "FQSaveToCache") VALUES
({d '2008-01-01'}, '1', '120000-933270541', 1.11,
'Test Future Dated Credit', 1)

INSERT INTO "JournalEntryDebitLine" ("TxnDate", "RefNumber",
"JournalDebitLineAccountRefListID", "JournalDebitLineAmount",
"JournalDebitLineMemo", "FQSaveToCache") VALUES
({d '2008-01-01'}, '1', '120000-933270541', 1.11,
'Test Future Dated Credit', 0)

without any problems here:

SELECT JournalCreditLineTxnLineID, JournalDebitLineTxnLineID
FROM JournalEntryCreditLine, JournalEntryDebitLine
WHERE JournalEntryCreditLine.RefNumber=JournalEntryDebitLine.RefNumber
and ((((JournalEntryDebitLine.TxnDate)>={d'2008-01-01'}))
or   (((JournalEntryCreditLine.TxnDate)>={d'2008-01-01'})))

The JournalEntry, JournalEntryCreditLine and JournalEntryDebitLine tables show the same entries as in Banking --> Make Jounal Entries in QuickBooks as they are the only "real" journals as QuickBooks doesn't have a General Ledger Transaction (GLTran) Table, which is your approach here.

QuickBooks stores the account reference in the sub-ledgers, so to change or modify anything you need to deal with it within the sub-ledger itself.

Intuit doesn't allow us access to Payroll Checks, so you can't use QODBC to change payroll liabilities such as payroll taxes, etc...

SELECT JournalEntryCreditLine.TxnDate, JournalEntryCreditLine.TxnID,
JournalEntryCreditLine.JournalCreditLineAccountRefFullName,
JournalEntryCreditLine.JournalCreditLineAmount,
JournalEntryDebitLine.JournalDebitLineAccountRefFullName,
JournalEntryDebitLine.JournalDebitLineAmount,
JournalEntryDebitLine.JournalDebitLineMemo
FROM JournalEntryCreditLine, JournalEntryDebitLine
WHERE JournalEntryCreditLine.TxnID=JournalEntryDebitLine.TxnID
and ((((JournalEntryDebitLine.TxnDate)>={d'2006-01-01'}))
or   (((JournalEntryCreditLine.TxnDate)>={d'2006-01-01'})))