Oracle 11g Release 2

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WITH t( timestamp, name ) AS
(
 SELECT date'2019-11-06','Jimmy'   FROM DUAL UNION ALL
 SELECT date'2019-11-06','Jack'    FROM DUAL UNION ALL
 SELECT date'2019-11-06','Sara'    FROM DUAL UNION ALL
 SELECT date'2019-11-07','Jimmy'   FROM DUAL UNION ALL
 SELECT date'2019-11-07','Jack'    FROM DUAL UNION ALL
 SELECT date'2019-11-07','Sara'    FROM DUAL UNION ALL
 SELECT date'2019-11-07','Michael' FROM DUAL UNION ALL
 SELECT date'2019-11-08','Don'     FROM DUAL UNION ALL
 SELECT date'2019-11-08','Alex'    FROM DUAL UNION ALL
 SELECT date'2019-11-08','Tina'    FROM DUAL UNION ALL
 SELECT date'2019-11-09','Jimmy'   FROM DUAL UNION ALL
 SELECT date'2019-11-09','Sara'    FROM DUAL 
)
SELECT NVL(t1.timestamp,t2.timestamp) AS timestamp, 
       SUM(NVL2(t1.timestamp,1,0)) AS new_names
  FROM (SELECT name, MIN(timestamp) AS timestamp from t group by name) t1
 RIGHT JOIN (SELECT DISTINCT timestamp FROM t) t2 
    ON t2.timestamp = t1.timestamp
 GROUP BY NVL(t1.timestamp,t2.timestamp)
 ORDER BY timestamp

TIMESTAMP	NEW_NAMES
06-NOV-19	3
07-NOV-19	1
08-NOV-19	3
09-NOV-19	0