Ado Parameter doesn't work with DateTime - need help

Hi

I'm using D6 with with an Interbase DB. I use MDAC 2.6 but on another computer
with 2.7 it didn't work either.
In the DB there are some datetime-fields.
When i try to set the Parameter, only the date will be stored in DB.
My program looks like this:
ADOQuery1.SQL.Text:= 'UPDATE .... SET SID_DATE = :SID_DATE';
ADOQuery.Paramater.ParamByName('SID_DATE').Value:= Now;
ExecSQL;

Then only the Date will be stored but i need the time too.
Even when i set the DataType of the parameter
ADOQuery.Parameter.ParamByName('SID_DATE').DataType:= ftDateTime;
it doesn't work.

Where I'm wrong?
Can someone help me please?