If NULL is allowed for a date field, a "blank" value will be considered as a null.
Otherwise, a blank value is be converted to "01.01.0001" when writing, and "01.01.0001" is converted to blank when reading.
See DATETYPE and TIMETYPE connection extended info for more details.
On SQL queries, when HQueryWithoutCorrection is used, *ISO format must be used: YYYY-MM-DD (2005-12-25) ; HH:MM:SS (17:59:59) .