Post Order

I needed to create multiple posts at once on my site. Since, without exception, the posts needed a published date earlier than when they were being created (oldest from 2013), I did my best to edit the “Published on” field in each one. Trying to verify if I had missed any found some with a 2013 date and some with a 2015 date, which is not my real problem. The problem is that, those with 2013 dates are not shown as the oldest. How can I fix this? Any help appreciated. Thanks!