Separate the trigger from the computed date
The most useful thing the workflow can extract is not the date. It is the structure: what event starts the period, how long the period is, what unit it uses, and which rule or order sets it. A draft entry that says "21 days after service of the motion, per paragraph 4 of the order" can be checked. A bare date cannot.
For each candidate entry, I would store the source document, the page, the quoted sentence, the trigger event, the period, and the proposed computed date as separate fields. When the trigger has not happened yet, the entry stays open rather than receiving a guessed date.