I want to create a Smart List that will pull in the actual date that someone has filled out a form. Currently, the "acquisition date" field is pulling in the date that the contact first had any activity and was added to our database. I know that I can use a Smart List to to filter for a certain time frame, but I want my report to show the actual date that an activity happened. Is there a field I can use for this?
To see it as an actual column in your report, no, there's no out-of-the-box field that will do this in your Smart List view.
If your form fill results in membership in a program, your best bet might be to go to the Members tab of the relevant program and include the Member Date column in your view.
Beyond that, you may want to look into setting up some custom fields to track historical activity. Lots of good examples in the community of stuff like this, but these will require some setup from you (and won't be able to help you retroactively, in this case).
(and won't be able to help you retroactively, in this case).
Well, if the activity took place in the past 90 days (for Filled Out Form) or is one of the long-lived activities, then an API extract could help w/backfill. But yes -- this is largely a "from this point forward" type of effort.