Short answer
HubSpot sets First conversion and First conversion date (the first form submitted) and Recent conversion and Recent conversion date (the latest) automatically. Companies have matching properties based on any associated contact. In my demo portal the date properties are date and time pickers.
1. The properties
Contact properties in my demo portal, searched for conversion date.

2. Use them
- Recent conversion date in the last 7 days: fresh leads view.
- First conversion: which form brought them in.