The Campaign Filters currently do not have a visible Create or Modify date, either in the UI or from the API.
Since the Campaign Filter can be created from the API in a manner that is not viewable in the Certification reports, and since it is used in Certifications it would be good to capture this from the API. Seeing as the filter could be modified between certification runs, it would be good to have the ability to output when the certification was added or updated (mostly updated) to record with the certification data.
Alternately, the Certification Composition Report could be updated to output all options for the filter, or in lieu of a nice way to output it, if the system decides it can not generate a pretty format, it should output the raw JSON with the report.