Database
[{"createdDate":ISODate("2022-10-01T02:00:00Z")},{"createdDate":ISODate("2022-10-01T02:00:00Z")},{"createdDate":ISODate("2022-10-02T02:00:00Z")},{"createdDate":ISODate("2022-10-03T02:00:00Z")},{"createdDate":ISODate("2022-10-06T02:00:00Z")},{"createdDate":ISODate("2022-10-07T02:00:00Z")}]
Query
db.collection.aggregate([{$group:{_id:{$dateTrunc:{date:"$createdDate",unit:"day"}},count:{$sum:1},},},{$set:{createdDate:"$_id"}},{$densify:{field:"createdDate",range:{step:1,unit:"day",bounds:"full"}}},{$fill:{sortBy:{createdDate:1},output:{count:{value:0}}}}])