ios - How do you properly order data from Firebase chronologically

Question

I'm trying to order my data from Firebase so the most recent post is at the top (like Instagram), but I just can't get it to work properly. Should I be using a server timestamp? Is there a "createdAt" field?

func getPosts() {
    POST_REF.observeEventType(.Value, withBlock: { snapshot in
        guard let posts = snapshot.value as? [String : [String : String]] else {
            print("No Posts Found")
            return
        }

        Post.feed?.removeAll()
        for (postID, post) in posts {
            let newPost = Post.initWithPostID(postID, postDict: post)!
            Post.feed?.append(newPost)
        }
        Post.feed? = (Post.feed?.reverse())!
        self.tableView.reloadData()
        }, withCancelBlock: { error in
            print(error.localizedDescription)
    })
}

Answer 1

Waitting for answers