Adding dates to engagement plan

I want to create engagement plans for our foundations.

We need to be able to have specific dates entered so that we know when to reach out for funding deadlines etc.

I started to create a plan but didn't see where to add dates.

It only has prompts for "Days after" etc.

I will be entering all of our foundations and hope to create a way that reminders for tasks can be sent on the specific dates we need.

Can anyone point me in a direction that makes sense?