Outputting date published time for IndieWeb microformat markup in Drupal 8

<\t\i\m\e \c\l\a\s\s="\d\t-p\ub\l\i\s\h\e\d" \d\a\t\e\t\i\m\e="c">Y F d</\t\i\m\e>

And in the preview shown after save, it looks great!

<time class="dt-published" datetime="2018-12-22T15:05:42-05:00">2018 December 22</time>

But in the source of something actually using it… it comes out like this:

2015 November 11

And this:

<\t\i\m\e \c\l\a\s\s="\d\t-p\ub\l\i\s\h\e\d" \d\a\t\e\t\i\m\e="Y-m-d h:m:i">Y F j</\t\i\m\e>

which previews like this:

<time class="dt-published" datetime="2018-12-22 03:12:16">2018 December 22</time>

ends up like this:

2015 November 11