Currently, campaign Blackout Dates can only be edited by the admin who created the entry.
If you would like admins with specific permissions to be able to edit Blackout Dates created by an admin (other then themselves) you'll want to reach out to your CSM to submit Product Feedback to inquire if this feature can be added to the Development Roadmap.
If further assistance is required, submit a ticket to Punchh Support. (For help submitting a ticket, click here)