this fixes #313

src/_locales/en/messages.json

@@ -523,6 +523,30 @@
     "message":"µBlock: Add the following URL to your custom filter lists?\n\nTitle: \"{{title}}\"\nURL: {{url}}",
     "description":"English: The message seen by the user to confirm subscription to a ABP filter list"
   },
+  "elapsedOneMinuteAgo":{
+    "message":"a minute ago",
+    "description":"English: a minute ago"
+  },
+  "elapsedManyMinutesAgo":{
+    "message":"{{value}} minutes ago",
+    "description":"English: {{value}} minutes ago"
+  },
+  "elapsedOneHourAgo":{
+    "message":"a hour ago",
+    "description":"English: a hour ago"
+  },
+  "elapsedManyHoursAgo":{
+    "message":"{{value}} hours ago",
+    "description":"English: {{value}} hours ago"
+  },
+  "elapsedOneDayAgo":{
+    "message":"a day ago",
+    "description":"English: a day ago"
+  },
+  "elapsedManyDaysAgo":{
+    "message":"{{value}} days ago",
+    "description":"English: {{value}} days ago"
+  },
   "dummy":{
     "message":"This entry must be the last one",
     "description":"so we dont need to deal with comma for last entry"

src/js/3p-filters.js

@@ -127,7 +127,9 @@ var renderBlacklists = function() {
 
         // In cache
         if ( asset.cached ) {
-            li.descendants('span.status.purge').css('display', '');
+            elem = li.descendants('span.status.purge');
+            elem.css('display', '');
+            elem.attr('title', renderElapsedTime(asset.lastModified));
             hasCachedContent = true;
         }
         return li;

src/js/i18n.js

@@ -20,6 +20,8 @@
 */
 
 /* global vAPI, uDom */
+/* exported renderElapsedTime */
+
 'use strict';
 
 /******************************************************************************/
@@ -46,3 +48,29 @@ uDom.onLoad(function() {
         );
     });
 });
+
+/******************************************************************************/
+
+var renderElapsedTime = function(tstamp) {
+    var value = (Date.now() - tstamp) / 60000;
+    if ( value < 2 ) {
+        return vAPI.i18n('elapsedOneMinuteAgo');
+    }
+    if ( value < 60 ) {
+        return vAPI.i18n('elapsedManyMinutesAgo').replace('{{value}}', Math.floor(value).toLocaleString());
+    }
+    value /= 60;
+    if ( value < 2 ) {
+        return vAPI.i18n('elapsedOneHourAgo');
+    }
+    if ( value < (24 * 60) ) {
+        return vAPI.i18n('elapsedManyHoursAgo').replace('{{value}}', Math.floor(value).toLocaleString());
+    }
+    value /= 24;
+    if ( value < 2 ) {
+        return vAPI.i18n('elapsedOneDayAgo');
+    }
+    return vAPI.i18n('elapsedManyDaysAgo').replace('{{value}}', Math.floor(value).toLocaleString());
+};
+
+/******************************************************************************/