如何在手机页面上集中博客发布日期/作者内容？

For whatever reason, I can't get this problem figured out; I'm trying to center my post's date and author contents on my mobile page. I can get the corresponding post title to center itself fine with "text-align: center" (which I'm not using currently, until the other issue is sorted out). For whatever reason, I can't get this problem f