The date() operator takes a string and converts it to a date.
date(“today”)
date(“today+7 days”)
In your case, evaluating “Today”+“7 Days” gives a result of “Today7 Days”, which Tinderbox can’t understand.
Suggestion: When puzzled by a date query like this, make a new Tinderbox file with a few notes. Select one, and make MyDate a key attribute. Type your date expression-- whatever text you’re feeding to date() – into the key attribute field.
Suggestion: When puzzled, ask here. You’re likely to get good advice on puzzles like this one, often very quickly.