Use JS Date().toLocaleDateString() to format date in header.

chrome/browser/resources/print_preview/print_preview_page.html

Index: chrome/browser/resources/print_preview/print_preview_page.html
diff --git a/chrome/browser/resources/print_preview/print_preview_page.html b/chrome/browser/resources/print_preview/print_preview_page.html
index 0eab31f0cd4f5e8a1f0e99b628afaafa4ffbbc05..d7a9de8e7237baa47a5fa8d26652fcfe42b505cc 100644
--- a/chrome/browser/resources/print_preview/print_preview_page.html
+++ b/chrome/browser/resources/print_preview/print_preview_page.html
@@ -73,8 +73,10 @@ function setup(options) {
                                 options['bottomMargin']);
   footer.style.height = pixels(options['bottomMargin']);
 
-  document.querySelector('#date span').innerText = options['date'];
+  document.querySelector('#date span').innerText =
+      new Date(options['date']).toLocaleDateString();
   document.querySelector('#title span').innerText = options['title'];
+
   document.querySelector('#url span').innerText = options['url'];
   document.querySelector('#page_number span').innerText = options['pageNumber'];