There’s more than one way to filter a table so I’m not sure exactly what you are doing. If you are using the dialog that says “Table Sort/Filter” at the top, then you’ll need to use a to_date expression (this is the best way to filter a large table because it will change the query and the filtering will be done by Oracle).
If you are using the grid’s built in filter, click on “Today” to see what format it expects, then change the value to whatever you need. (This way is probably easier to set up, but it does not limit the data that comes out of the database and to your computer - the grid just hides the non-matching rows. This is fine for small tables, but it can cause all rows to be loaded into memory on your computer, so you don’t want to do this with large tables)