Date

It'd be more helpful if your subject line could be more than one word, for future reference.

To give a date a particular formatting in text when using for read-only purposes, you will use the text() function, which accepts a value and a formatting.

Additionally, if your text field is Read-Only, there is no need to set a "saveInto" as the save will never be executed when the field is read-only.  If you need to set the rule input value to the value "today()", you will need to include this within a saveInto of a component the user interacts with.