From e54112c8459cd7ee0c4b68b59e930114bd3f38ce Mon Sep 17 00:00:00 2001
From: Masataka Yakura <masataka.yakura@gmail.com>
Date: Mon, 8 May 2023 21:31:11 +0900
Subject: [PATCH] add `datetime` attributes to `<time>` elements (#3630)

Currently dates are marked up using `<time>` but they lack `datetime` attributes.
The HTML spec requires that the date value to be machine-readable; either the text content follows the valid date string (ISO-like patterns), or the element has the `datetime` attribute where the value is a valid date string.
https://whatwg.org/html#the-time-element

Co-authored-by: Matthias Rohmer <mrohmer@google.com>
---
 site/_includes/partials/post-headline.njk | 8 ++++++--
 site/_includes/partials/updated.njk       | 4 ++--
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/site/_includes/partials/post-headline.njk b/site/_includes/partials/post-headline.njk
index 54c1e8270b3d..486e90578c35 100644
--- a/site/_includes/partials/post-headline.njk
+++ b/site/_includes/partials/post-headline.njk
@@ -7,11 +7,15 @@
 {% if date %}
   <p class="type--caption color-secondary-text">
     {{ 'i18n.common.published_on' | i18n(locale) }}
-    <time>{{ helpers.formatDateLong(date, locale) }}</time>
+    <time datetime="{{ helpers.formatDateNumeric(date) }}">
+      {{ helpers.formatDateLong(date, locale) }}
+    </time>
     {% if updated %}
     <span>•</span>
     {{ 'i18n.common.updated_on' | i18n(locale) }}
-    <time>{{ helpers.formatDateLong(updated, locale) }}</time>
+    <time datetime="{{ helpers.formatDateNumeric(updated) }}">
+      {{ helpers.formatDateLong(updated, locale) }}
+    </time>
   {% endif %}
   </p>
 {% endif %}
diff --git a/site/_includes/partials/updated.njk b/site/_includes/partials/updated.njk
index 7f8c6fe97a53..ac467137d697 100644
--- a/site/_includes/partials/updated.njk
+++ b/site/_includes/partials/updated.njk
@@ -1,9 +1,9 @@
 <p class="color-secondary-text type--caption">
   {% if updated %}
-    {{ 'i18n.common.updated_on' | i18n(locale) }} <time>{{ helpers.formatDateLong(updated, locale) }}</time>
+    {{ 'i18n.common.updated_on' | i18n(locale) }} <time datetime="{{ helpers.formatDateNumeric(updated) }}">{{ helpers.formatDateLong(updated, locale) }}</time>
     <span>•</span>
   {% elif date %}
-    {{ 'i18n.common.updated_on' | i18n(locale) }} <time>{{ helpers.formatDateLong(date, locale) }}</time>
+    {{ 'i18n.common.published_on' | i18n(locale) }} <time datetime="{{ helpers.formatDateNumeric(date) }}">{{ helpers.formatDateLong(date, locale) }}</time>
     <span>•</span>
   {% endif %}
   <a href="{{ page.inputPath | githubLink }}">