Is there an audit trail of who created or changed a rule, or a history I can query?

No.

Nothing records who created or edited a rule, and the API works on rules rather than on a history of what the app did with them, so past absences cannot be reported on through it.

What exists is the Creator column on the rules table and each rule's Reassignment Log.

Related pages

• Analytics and Reporting with Out of Office Data - where this is covered in full.

• Automations and Workflow - more questions on this topic.