Write SQL query to solve given problem: When did event number 7 happen for user number -8022267440849930000?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T1.timestamp FROM events_relevant AS T1 INNER JOIN app_events AS T2 ON T1.event_id = T2.event_id WHERE T2.app_id = -8022267440849930000 AND T1.event_id = 7