Subtract days from date automation

I need an automation that creates the internal due date based on a pre-populated deliverable date, something like:

When an item is created, set DATE1 to X DAYS before DATE2.

Date 1 is an internal due date and Date 2 is the client deliverable date. X Days is the number of business days we have to complete the task.

This needs to work with items that are created via integrations (Monday Forms for example) where DATE2 will come in populated with a date during item creation.

Thanks!