Blog publish date via API or RSS feed

Is there any way to find out publish date of any blog post via an API call to the respective wordpress blog (without authentication) or from (comments)RSS feed of that blog post?

For example, in case of a Blogger.com blog post, like – https://googleblog.blogspot.com/2010/04/this-week-in-search-41610.html, if you view the comments RSS feed – https://googleblog.blogspot.com/feeds/5151703838339713598/comments/default, the channel has a subtag – updated, that i think shows when the blog post last updated. With this information, it becomes very easy to index old blog posts without the need to build a custom html parser to determine the blog post time for any given post.