[{"_id":"9d78d0e8-7b13-4487-88a3-d91d64f29b38","Number":"001","createdon":{"$date":"2019-09-19T00:00:00.000Z"}},{"_id":"5d78d0e8-7b13-4487-88a3-d91d64f29b02","Number":"002","createdon":{"$date":"2019-09-13T00:00:00.000Z"}},{"_id":"2w78d0e8-7b13-4487-88a3-d91d64f29b47","Number":"003","createdon":{"$date":"2019-09-25T00:00:00.000Z"}},{"_id":"6e78d0e8-7b13-4487-88a3-d91d64f29b2d","Number":"004","createdon":{"$date":"2020-01-18T00:00:00.000Z"}}]

db.collection.aggregate([{$sort:{createdon:-1}},{$addFields:{createdon:{$dateToString:{date:"$createdon",format:"%Y-%m-%d"}}}}])