1. In Banks, click Open Bank Register
2. Locate the check and open it
3. At the bottom of the General tab, the Reversal status/date shows the void status and the date of the void
4. Click the Red "X" to exit out of the check, and when prompted to save the check, click Save

Note: If the check has a post status of Do no post, you will not be able to edit the reversal date, as the original check never posted to the General Ledger.