There is no automatic way to do this. If you look at your the “My Awards” page you can see you qualify for the Mountain Hunter Amethyst award. To qualify you need to have chased 2 summits in 30 associations and 4 continents. My Awards shows the associations that qualify, you need a copy of this table. You can look at My Chaser Uniques and click Association. This sorts by association. You then need to find the dates of the first 2 summits in each association chased, use the list of associations you saved. You should be able to quite quickly find when you qualified.
If you don’t want to do this you can put the date you applied for the certificate in the form.