[Zope] Problems with date format

When I input a date in a DTML Form, I use the "%d/%m/%Y" format, but that date field must be stored in a MS SQL Server database in "%m/%d/%Y" format. I've tried to store that field using: <dtml-sqlvar date_field.strftime('%m/%d/%Y') type=string> but an error ocurred. How can I do that ? Thanks for any help.