In response to #1, use jekyll-last-modified-at gem to report last update for each page on build.

aepstein · aepstein · commit 1fcb4efa2703 · 2015-02-05T07:09:38.000-05:00
diff --git a/_config.yml b/_config.yml
@@ -0,0 +1,2 @@
+gems:
+  - jekyll-last-modified-at
diff --git a/_layouts/default.html b/_layouts/default.html
@@ -3,7 +3,7 @@
 <title>Open Data Resources</title>
 </head>
 <body>
-(last updated: {{ post.date | date: '%B %d, %Y' }} )
+(last updated: {{ page.last_modified_at | date: '%B %d, %Y' }} )
 <hr />
 {{content}}
 </body>
