diff --git a/lib/shared/thread-utils.js b/lib/shared/thread-utils.js
--- a/lib/shared/thread-utils.js
+++ b/lib/shared/thread-utils.js
@@ -1177,6 +1177,17 @@
   return null;
 }
 
+function useLastActiveTime(item: ChatThreadItem): number {
+  const lastUpdatedTimes = item.sidebars.map(sidebar => {
+    if (sidebar.type === 'sidebar') {
+      return sidebar.lastUpdatedTime;
+    } else {
+      return 0;
+    }
+  });
+  return Math.max(item.lastUpdatedTime, ...lastUpdatedTimes);
+}
+
 export {
   colorIsDark,
   generateRandomColor,
@@ -1231,4 +1242,5 @@
   threadTypeCanBePending,
   getContainingThreadID,
   getCommunity,
+  useLastActiveTime,
 };
diff --git a/web/chat/chat-thread-list-item.react.js b/web/chat/chat-thread-list-item.react.js
--- a/web/chat/chat-thread-list-item.react.js
+++ b/web/chat/chat-thread-list-item.react.js
@@ -5,6 +5,7 @@
 
 import type { ChatThreadItem } from 'lib/selectors/chat-selectors';
 import { useAncestorThreads } from 'lib/shared/ancestor-threads';
+import { useLastActiveTime } from 'lib/shared/thread-utils';
 import { shortAbsoluteDate } from 'lib/utils/date-utils';
 
 import { useSelector } from '../redux/redux-utils';
@@ -23,15 +24,16 @@
   +item: ChatThreadItem,
   +setModal: (modal: ?React.Node) => void,
 };
+
 function ChatThreadListItem(props: Props): React.Node {
   const { item, setModal } = props;
   const { threadInfo } = item;
   const threadID = item.threadInfo.id;
   const ancestorThreads = useAncestorThreads(threadInfo);
   const onClick = useOnClickThread(threadID);
-
   const timeZone = useSelector(state => state.timeZone);
-  const lastActivity = shortAbsoluteDate(item.lastUpdatedTime, timeZone);
+  const rawLastActivity = useLastActiveTime(item);
+  const lastActivity = shortAbsoluteDate(rawLastActivity, timeZone);
 
   const active = useThreadIsActive(threadID);
   const containerClassName = React.useMemo(