If you're not getting any error in search console, then you don't need to change rss format or something like that. If you set any attribute like dates in Rss, then Google will simply ignore it, because many of people misused everyday.
Any dates attribute on rss/sitemap/article does not change crawling rate for specific webpage. Once Google recrawl that webpage then Google will update that dates in their search result as snippet.
Crawlers are not real time, it take few days to crawl your webpages. You have to wait it for few days. Sites like wikipedia crawl often because many of people link them (It means if you have more links(PageRank) the more times crawler will come to your website).
Other websites also crawl automatically without using fetch and render tools, because people really enjoy that stuff. Google somehow find out those webpages automatically even those pages are not linked from anywhere.
You should read these answers as well: