Among the dishes, how many of them were created between 2011-03-31 at 20:24:46 UTC and 2011-04-15 at 23:09:51 UTC.
created between 2011-03-31 at 20:24:46 UTC and 2011-04-15 at 23:09:51 UTC refers to created_at between '2011-03-31 20:24:46 UTC' AND '2011-04-15 23:09:51 UTC';
SELECT SUM(CASE WHEN T2.created_at BETWEEN '2011-03-31 20:24:46 UTC' AND '2011-04-15 23:09:51 UTC' THEN 1 ELSE 0 END) FROM Dish AS T1 INNER JOIN MenuItem AS T2 ON T1.id = T2.dish_id