From 248fcaaabf88e0f95e5426889a85b94f012f1593 Mon Sep 17 00:00:00 2001
From: Miki <miki@amazon.com>
Date: Fri, 14 Apr 2023 09:03:52 -0700
Subject: [PATCH] Use the modified dates of files in the sitemap (#3774)

* The extracted dates are also added as a comment to the `head` of HTML pages

Signed-off-by: Miki <miki@amazon.com>
---
 Gemfile                    | 4 +++-
 _config.yml                | 5 +++++
 _includes/head_custom.html | 2 ++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/Gemfile b/Gemfile
index cd42fda502..8a1a31f619 100644
--- a/Gemfile
+++ b/Gemfile
@@ -22,6 +22,7 @@ gem "jekyll-redirect-from", "~> 0.16"
 
 # If you have any plugins, put them here!
 group :jekyll_plugins do
+  gem "jekyll-last-modified-at"
   gem "jekyll-sitemap"
 end
 
@@ -34,6 +35,7 @@ gem "wdm", "~> 0.1.0" if Gem.win_platform?
 # Installs webrick dependency for building locally
 gem "webrick", "~> 1.7"
 
+
 # Link checker
 gem "typhoeus"
-gem "ruby-link-checker"
\ No newline at end of file
+gem "ruby-link-checker"
diff --git a/_config.yml b/_config.yml
index f99b1f3905..f69efb79fa 100644
--- a/_config.yml
+++ b/_config.yml
@@ -202,10 +202,15 @@ anchor_links: true
 footer_content:
 
 plugins:
+  - jekyll-last-modified-at
   - jekyll-remote-theme
   - jekyll-redirect-from
   - jekyll-sitemap
 
+# This format has to conform to RFC822
+last-modified-at:
+  date-format: '%a, %d %b %Y %H:%M:%S %z'
+
 # Exclude from processing.
 # The following items will not be processed, by default. Create a custom list
 # to override the default setting.
diff --git a/_includes/head_custom.html b/_includes/head_custom.html
index 1a18be03bb..a6bc7b7a3b 100755
--- a/_includes/head_custom.html
+++ b/_includes/head_custom.html
@@ -12,3 +12,5 @@
 {% else %}
   <script src="{{ '/docs/latest/assets/js/version-selector.js' }}"></script>
 {% endif %}
+
+<!-- Last-Modified: {% last_modified_at %} -->