In the Customer database, if you want to filter only the people who did a certain action during a specific time, you can do it from the time frame picker available for all action-based filters (these are Actions performed, Actions not performed, Product interactions Product categories, Mail campaigns and Coupons used).
The option Pick a time frame becomes active after you choose the filter and lets you select
- a dynamic period (relative to the current date like 10 days ago)
- a fixed period of time (from date to date) on the calendar.
This way you're filtering only the people who did the action during the chosen period. If you want the all-time qualifiyng customers, just don't use the time frame option.