The dates showing in the Import Wizard's data preview window are not the same that were imported to the table.
Waiting for fix to be released in a future version of Toad for Oracle.
One reason that the dates on the Excel spreadsheet and in the Import Wizard's data preview window can be different from what is actually imported is that there is a space in the cell before the date. Removing the space or setting the date format in the wizard seemed to resolve the issue. You can set the data format on the 3rd screen (Specify Source Data Details) as 'mm/dd/yyyy', then the data will be imported correctly. You have to set the Date Order drop down to 'custom' before setting the format. If Ã¢â‚mm/dd/yyyyyyÃ¢â‚ is not an option for you in the drop down, you can manually type it in.