Write SQL query to solve given problem: How many OPPO users participated in events which were held around 12 AM on 1st May,2016?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT COUNT(T1.device_id) FROM events AS T1 INNER JOIN phone_brand_device_model2 AS T2 ON T1.device_id = T2.device_id WHERE T2.phone_brand = 'OPPO' AND STRFTIME('%Y-%m-%d', T1.`timestamp`) = '2016-05-01'