Hi,
My understanding is that you want to trigger intermediate timer event based on calculation of difference between my variable ${date} and today's date. If that is the scenario then you can set calculated dynamic duration (in minutes) in a variable. Pass that variable(e.g. ${duration})in formula section of Intermediary event.
e.g ${(((due_date?number) - timestamp("SECOND")?number)/60)?string("0")?number}
where due date is numeric data variable coming from WI.
${timestamp(unit} is a freemarker script to get a timestamp.
Refer below tutorials for more info -
Hope this helps you.