partial revert of a9984bb, adding in a layer to translate ISO

timestamp to datetime attribute and save localised string into
title attribute.

Fixes #5109

public/src/overrides.js

@@ -152,13 +152,18 @@ if ('undefined' !== typeof window) {
 		var timeagoFn = $.fn.timeago;
 		$.timeago.settings.cutoff = 1000 * 60 * 60 * 24 * 30;
 		$.fn.timeago = function () {
-			var els = timeagoFn.apply(this, arguments);
+			var els = $(this);
+
+			// Convert "old" format to new format (#5108)
+			var options = { year: 'numeric', month: 'long', day: 'numeric' };
+			var iso;
+			els.each(function() {
+				iso = this.getAttribute('title');
+				this.setAttribute('datetime', iso);
+				this.setAttribute('title', new Date(iso).toLocaleString(config.userLang.replace('_', '-'), options));
+			});
 
-			if (els) {
-				els.each(function () {
-					$(this).attr('title', (new Date($(this).attr('title'))).toString());
-				});
-			}
+			timeagoFn.apply(this, arguments);
 		};
 	};
 

public/vendor/jquery/timeago/jquery.timeago.js

@@ -194,41 +194,7 @@
         $(this).text(inWords(data.datetime));
       } else {
         if ($(this).attr('title').length > 0) {
-            //$(this).text($(this).attr('title'));
-            var languageCode = void 0;
-            switch (config.userLang) {
-              case 'en_GB':
-              case 'en_US':
-                languageCode = 'en';
-                break;
-
-              case 'fa_IR':
-                languageCode = 'fa';
-                break;
-
-              case 'pt_BR':
-                languageCode = 'pt-br';
-                break;
-
-              case 'nb':
-                languageCode = 'no';
-                break;
-
-              case 'zh_TW':
-                languageCode = 'zh-TW';
-                break;
-
-              case 'zh_CN':
-                languageCode = 'zh-CN';
-                break;
-
-              default:
-                languageCode = config.userLang;
-                break;
-            }
-
-            var options = { year: 'numeric', month: 'long', day: 'numeric' };
-            $(this).text(new Date($(this).attr('title')).toLocaleString(languageCode, options));
+            $(this).text($(this).attr('title'));
         }
       }
     }