This is the real-time feed of your account. The Activity Log shows entries of most transactions your firm's users are working on.
When you click on Advanced Search, the By Date field shows a "Recent" option. The recent items are those in the last 300 days. If you want to see a date range farther in the past, choose Custom Range and enter an older From date.
You can create time entries from an item by clicking the green clock icon on its row. If a Matter is associated with the entry, it will default to that matter and then allow you to record the specific time entry details for that activity.