Auto-Creation of Tasks Leading up to a Specific Date Field (ie due 150 days Before Date)

Hello, trying to figure out if this is possible within Process Definition or if needs to be coded.

I'm trying to set off a chain of tasks that need to be created based on a date in the future. For example, let's say an annual conference event date field is filled in a specific module.

Using this annual conference event date, I want tasks to be created leading up to the event. For example, 150 days before the conference a task is created to send out invitations, then 100 days leading up to the event a task is created to book a musician, then 50 days leading up to the event a task is created to order all the decor.

So the triggering event for the tasks will be based on a future date.

There are tons of ways to schedule tasks to be created from a date + so many minutes, days, or what have you; but I can't find a way to schedule tasks leading up to a date.

One solution I thought of was to have a separate hidden field that automatically subtracts the maximum days from the event date, then using that calculated date to build a Process Definition.

Has anyone ever needed to created start events based on a future date? How did you go about designing the solution? I'm using Enterprise 7.8. Thank you for any help or insight!