Hi Marcelo,
You can change the date to a few fixed formats but unfortunately not the format you requested. If you click the Advanced options on the date field when editing the grid you can switch from Date, Time, or Date and Time.
What you can do is use the Date Function action to populate a new field with the day of the week, if this is what you need, but you cannot add the day of the week directly to the date field.
- Jason