Date data types don’t support numerical operators lke you’re showing here. And currently relative dates aren’t supported. Development would have to assess this.
If the documents you want this to act on are not madly numerous, a script could do what you’re looking to do. You could trigger the script to run once a day on documents which contain an event date, for example.
In fact, you may be able to limit the smart rule to something along the lines of today AND/OR last week AND/OR this week, meaning that the script wouldn’t have to go through so many documents.
Your script would then add or remove a tag, which you could use as a condition for the smart group