This post is for future posts.
Check the lines 5 to 9 of my post template head.html.
<meta name="generator" content="blogger"/>
<meta name="author" content="Sau-Chin Chen"/>
# A if-then loop imports page.title.
<meta property="og:title" content="{% if page.title %}{{ page.title }}{% else %}{{ site.title }}{% endif %}"/>
# A if-then loop imports page.date.
<meta property="article:published_time" content="{% if page.date %}{{ page.date | date: "%B %-d, %Y"}}{% else %}{{ site.date }}{% endif %}"/>
<meta property="og:site_name" content="Sau-Chin Chen's website"/>