Can't sort by date node was created in Views?

I create a view and created a block in the view so that I have a block of the latest documents/nodes created for a specific document type, Let's call it medical news and every node/post will be sorted with the newest on top and in reverse chronological order. Now to sort the results, I see there are existing indexes and also something called "relevance" for the search. But I can't sort by the date the document was created / posted / modified. For example, this field:

Indexed Node: Date created
The date the node was posted.

I added this Indexed Node field as a hidden field to the fields in the view. We don't want it to appear, just be included. Yet the Sort does not include this field for sorting purposes. Nor can I use the date modified either.