Audit report event timestamps are displayed in the HH:MM:SS format, always within the range of 00:00:00 to 12:59:59, but without any AM or PM indication.
This is a known issue and a defect request was submitted to fix the issue on a future release of Active Adminsitrator.
Defect ID: 568553
Note: When viewing the details of an event, the timestamp is displayed correctly based on the time format used by the domain controller where the event was generated... showing AM/PM in 12-hour format or times like 09:40 / 18:40 in 24-hour format.