On landing pages ? Or you mean in the lead database, knowing when someone has filled out a registration form ?
If this is the second choice, you will need to log the date/time in a dedicated field so that you can display the information and export it from a smart list.
You can also filter on the date, using date constraints on the "filled out form" filter.
Please move the thread to Products (move link at the right). This isn't a support space.