header element is rendered in lib.stdheader for all cases
According to the HTML5 spec the header element represents
a group of introductory or navigational aids. A header element typically contains the section’s heading (an h1–h6 element or an hgroup element), but can also contain other content, such as a table of contents, a search form, or any relevant logos.
First of all, the hgroup element has been removed from the specs.
Secondly, header is used to group elements. Currently the header element is used if there is any content in lib.stdheader, so for instance with a single hx. This is not desired because a single element is not a group.
Wrapping lib.stdheader with the header element should only occur when the date is added to the header.