There's nothing directly from the UI available to accomplish this. You'll have to get if from a database query:
# dbc 'select * from license_history;' >> /tmp/amp_license_history.txt
The time associated to the license will be in epoch time, but you can easily change that to human readable form with epoch2timestamp
Example:
[root@rob ~]# dbc 'select * from license_history'
id | product_version | accepted_by | license | accepted_on
----+-----------------+-------------+------------------------------------------------------------------+-------------
1 | 7.7.10 | admin | --- Begin AMP License Key --- +| 1411578638
[root@rob ~]# epoch2timestamp 1411578638
Wed Sep 24 13:10:38 EDT 2014
From the above, I know that the admin user applied this license on 9/24 @ 1pm ET. This table only catches licenses added (changing a license shows as a new row in that table). It will not reflect deletes.