AppleScript to erase and replace text file content

Thanks so much! That worked perfectly. To insert the date at the start, here was the final AppleScript:

set date_ to do shell script "date +'%Y-%m-%d'"
tell application id "DNtp" --------------------------Retrieve the DT data
	set theDailyNote to (get record with uuid "8B2C1362-D4F5-4BD2-806D-7C7DD4F527BA")
	set theNewContents to date_
	set plain text of theDailyNote to theNewContents
end tell