You can add events to a matter through the CalendarRules integration. 

How to Add a CalendarRules Event to a Matter

1. Log in to Litify.
2. Navigate to Matters > [Matter Name]. 
3. Navigate to the CalendarRules tab.
   
4. Choose a Jurisdiction.
5. Choose a Trigger Item. 
6. Provide a Date.
7. Select Get Events to see applicable events.
   
8. Enable the checkbox of each event you want to add to the calendar.
9. Select Add to Calendar. 

The events are then added to the matter owner's calendar.