diff --git a/static/js/feature_flags.js b/static/js/feature_flags.js
index 6d1da28c77..c8510272bd 100644
--- a/static/js/feature_flags.js
+++ b/static/js/feature_flags.js
@@ -5,7 +5,8 @@ var exports = {};
 exports.always_open_compose =  true;
 exports.mark_read_at_bottom = page_params.staging;
 exports.summarize_read_while_narrowed = page_params.staging;
-
+exports.twenty_four_hour_time = _.contains([],
+                                  page_params.email);
 return exports;
 
 }());
diff --git a/static/js/message_list.js b/static/js/message_list.js
index a89ae1b2a8..90a810e28c 100644
--- a/static/js/message_list.js
+++ b/static/js/message_list.js
@@ -53,7 +53,10 @@ function add_display_time(message, prev) {
     }
 
     if (message.timestr === undefined){
-        message.timestr = time.toString("HH:mm");
+        message.timestr = time.toString("h:mmtt");
+        if (feature_flags.twenty_four_hour_time) {
+            message.timestr = time.toString("HH:mm");
+        }
     }
 }