set plngHours to 19 -- e.g. 7pm

tell application id "OFOC"
	tell default document
		set lstTasks to flattened tasks where (due date is not missing value)
		repeat with oTask in lstTasks
			set dteDue to due date of oTask
			if hours of dteDue = 0 and minutes of dteDue = 0 then
				set dteDue to (dteDue - days) -- previous day
				set hours of dteDue to plngHours
				set due date of oTask to dteDue
			end if
		end repeat
	end tell
end tell