diff --git a/common/static/coffee/spec/discussion/view/discussion_thread_list_view_spec.coffee b/common/static/coffee/spec/discussion/view/discussion_thread_list_view_spec.coffee
index af89d01a6c..e27436bc01 100644
--- a/common/static/coffee/spec/discussion/view/discussion_thread_list_view_spec.coffee
+++ b/common/static/coffee/spec/discussion/view/discussion_thread_list_view_spec.coffee
@@ -88,7 +88,7 @@ describe "DiscussionThreadListView", ->
                     <% } %>
                     <label class="forum-nav-sort">
                         <select class="forum-nav-sort-control">
-                            <option value="date">by recent activity</option>
+                            <option value="activity">by recent activity</option>
                             <option value="comments">by most activity</option>
                             <option value="votes">by most votes</option>
                         </select>
@@ -232,8 +232,8 @@ describe "DiscussionThreadListView", ->
                     )
                 ).toEqual(["+25 votes", "+20 votes", "+42 votes", "+12 votes"])
 
-        it "with sort preference date", ->
-            checkRender(@threads, "date", ["Thread1", "Thread4", "Thread2", "Thread3"])
+        it "with sort preference activity", ->
+            checkRender(@threads, "activity", ["Thread1", "Thread2", "Thread3", "Thread4"])
 
         it "with sort preference votes", ->
             checkRender(@threads, "votes", ["Thread4", "Thread1", "Thread2", "Thread3"])
@@ -249,7 +249,7 @@ describe "DiscussionThreadListView", ->
         sortControl = view.$el.find(".forum-nav-sort-control")
         expect(sortControl.val()).toEqual(selected_type)
         sorted_threads = []
-        if new_type == 'date'
+        if new_type == 'activity'
           sorted_threads = [threads[0], threads[3], threads[1], threads[2]]
         else if new_type == 'comments'
           sorted_threads = [threads[0], threads[3], threads[2], threads[1]]
@@ -265,11 +265,11 @@ describe "DiscussionThreadListView", ->
         expect($.ajax).toHaveBeenCalled()
         checkThreadsOrdering(view, sort_order, new_type)
 
-      it "with sort preference date", ->
-          changeSorting(@threads, "comments", "date", ["Thread1", "Thread4", "Thread2", "Thread3"])
+      it "with sort preference activity", ->
+          changeSorting(@threads, "comments", "activity", ["Thread1", "Thread4", "Thread3", "Thread2"])
 
       it "with sort preference votes", ->
-          changeSorting(@threads, "date", "votes", ["Thread4", "Thread1", "Thread2", "Thread3"])
+          changeSorting(@threads, "activity", "votes", ["Thread4", "Thread1", "Thread2", "Thread3"])
 
       it "with sort preference comments", ->
           changeSorting(@threads, "votes", "comments", ["Thread1", "Thread4", "Thread3", "Thread2"])
diff --git a/common/static/coffee/src/discussion/discussion.coffee b/common/static/coffee/src/discussion/discussion.coffee
index 99378e1f12..c674ae9c88 100644
--- a/common/static/coffee/src/discussion/discussion.coffee
+++ b/common/static/coffee/src/discussion/discussion.coffee
@@ -20,7 +20,7 @@ if Backbone?
 
     setSortComparator: (sortBy) ->
       switch sortBy
-        when 'date' then @comparator = @sortByDateRecentFirst
+        when 'activity' then @comparator = @sortByDateRecentFirst
         when 'votes' then @comparator = @sortByVotes
         when 'comments' then @comparator = @sortByComments
 
@@ -49,7 +49,7 @@ if Backbone?
           url = DiscussionUtil.urlFor 'followed_threads', options.user_id
       if options['group_id']
         data['group_id'] = options['group_id']
-      data['sort_key'] = sort_options.sort_key || 'date'
+      data['sort_key'] = sort_options.sort_key || 'activity'
       data['sort_order'] = sort_options.sort_order || 'desc'
       DiscussionUtil.safeAjax
         $elem: @$el
@@ -117,8 +117,9 @@ if Backbone?
 
     pinnedThreadsSortComparatorWithDate: (thread, ascending)->
       # if threads are pinned they should be displayed on top.
-      # Unpinned will be sorted by their date
+      # Unpinned will be sorted by their last activity date
       threadCreatedTime = new Date(thread.get("created_at")).getTime()
+      threadCreatedTime = new Date(thread.get("last_activity_at")).getTime()
       if thread.get('pinned')
         #use tomorrow's date
         today = new Date();
diff --git a/common/static/coffee/src/discussion/views/discussion_thread_list_view.coffee b/common/static/coffee/src/discussion/views/discussion_thread_list_view.coffee
index 512df63405..502d4e377e 100644
--- a/common/static/coffee/src/discussion/views/discussion_thread_list_view.coffee
+++ b/common/static/coffee/src/discussion/views/discussion_thread_list_view.coffee
@@ -161,7 +161,7 @@ if Backbone?
       voteCounts.hide()
       commentCounts.hide()
       switch @$(".forum-nav-sort-control").val()
-        when "date", "comments"
+        when "activity", "comments"
           commentCounts.show()
         when "votes"
           voteCounts.show()
diff --git a/common/test/acceptance/tests/discussion/test_discussion.py b/common/test/acceptance/tests/discussion/test_discussion.py
index 2eed018bdc..9b0f7c7775 100644
--- a/common/test/acceptance/tests/discussion/test_discussion.py
+++ b/common/test/acceptance/tests/discussion/test_discussion.py
@@ -1121,14 +1121,14 @@ class DiscussionSortPreferenceTest(UniqueCourseTest):
         Test to check the default sorting preference of user. (Default = date )
         """
         selected_sort = self.sort_page.get_selected_sort_preference()
-        self.assertEqual(selected_sort, "date")
+        self.assertEqual(selected_sort, "activity")
 
     def test_change_sort_preference(self):
         """
         Test that if user sorting preference is changing properly.
         """
         selected_sort = ""
-        for sort_type in ["votes", "comments", "date"]:
+        for sort_type in ["votes", "comments", "activity"]:
             self.assertNotEqual(selected_sort, sort_type)
             self.sort_page.change_sort_preference(sort_type)
             selected_sort = self.sort_page.get_selected_sort_preference()
@@ -1139,7 +1139,7 @@ class DiscussionSortPreferenceTest(UniqueCourseTest):
         Test that user last preference is saved.
         """
         selected_sort = ""
-        for sort_type in ["votes", "comments", "date"]:
+        for sort_type in ["votes", "comments", "activity"]:
             self.assertNotEqual(selected_sort, sort_type)
             self.sort_page.change_sort_preference(sort_type)
             selected_sort = self.sort_page.get_selected_sort_preference()
diff --git a/lms/djangoapps/discussion_api/tests/utils.py b/lms/djangoapps/discussion_api/tests/utils.py
index e341443a24..5abd82f563 100644
--- a/lms/djangoapps/discussion_api/tests/utils.py
+++ b/lms/djangoapps/discussion_api/tests/utils.py
@@ -332,6 +332,7 @@ def make_minimal_cs_thread(overrides=None):
         "anonymous_to_peers": False,
         "created_at": "1970-01-01T00:00:00Z",
         "updated_at": "1970-01-01T00:00:00Z",
+        "last_activity_at": "1970-01-01T00:00:00Z",
         "thread_type": "discussion",
         "title": "dummy",
         "body": "dummy",
diff --git a/lms/djangoapps/django_comment_client/forum/views.py b/lms/djangoapps/django_comment_client/forum/views.py
index 1459d4c39c..dace54e169 100644
--- a/lms/djangoapps/django_comment_client/forum/views.py
+++ b/lms/djangoapps/django_comment_client/forum/views.py
@@ -94,7 +94,7 @@ def get_threads(request, course, discussion_id=None, per_page=THREADS_PER_PAGE):
     default_query_params = {
         'page': 1,
         'per_page': per_page,
-        'sort_key': 'date',
+        'sort_key': 'activity',
         'sort_order': 'desc',
         'text': '',
         'course_id': unicode(course.id),
diff --git a/lms/djangoapps/django_comment_client/utils.py b/lms/djangoapps/django_comment_client/utils.py
index 21730c0bcb..16e3d3baab 100644
--- a/lms/djangoapps/django_comment_client/utils.py
+++ b/lms/djangoapps/django_comment_client/utils.py
@@ -654,7 +654,7 @@ def prepare_content(content, course_key, is_staff=False, course_is_cohorted=None
         'read', 'group_id', 'group_name', 'pinned', 'abuse_flaggers',
         'stats', 'resp_skip', 'resp_limit', 'resp_total', 'thread_type',
         'endorsed_responses', 'non_endorsed_responses', 'non_endorsed_resp_total',
-        'endorsement', 'context'
+        'endorsement', 'context', 'last_activity_at'
     ]
 
     if (content.get('anonymous') is False) and ((content.get('anonymous_to_peers') is False) or is_staff):
diff --git a/lms/lib/comment_client/thread.py b/lms/lib/comment_client/thread.py
index 4316b97122..625711ace6 100644
--- a/lms/lib/comment_client/thread.py
+++ b/lms/lib/comment_client/thread.py
@@ -20,7 +20,7 @@ class Thread(models.Model):
         'highlighted_body', 'endorsed', 'read', 'group_id', 'group_name', 'pinned',
         'abuse_flaggers', 'resp_skip', 'resp_limit', 'resp_total', 'thread_type',
         'endorsed_responses', 'non_endorsed_responses', 'non_endorsed_resp_total',
-        'context',
+        'context', 'last_activity_at',
     ]
 
     # updateable_fields are sent in PUT requests
diff --git a/lms/templates/discussion/_thread_list_template.html b/lms/templates/discussion/_thread_list_template.html
index 4af6dbe7c7..e6b29d06e5 100644
--- a/lms/templates/discussion/_thread_list_template.html
+++ b/lms/templates/discussion/_thread_list_template.html
@@ -54,7 +54,7 @@
                 <span class="sr">${_("Sort:")}</span>
                 <select class="forum-nav-sort-control">
                     ## Translators: This is a menu option for sorting forum threads
-                    <option value="date">${_("by recent activity")}</option>
+                    <option value="activity">${_("by recent activity")}</option>
                     ## Translators: This is a menu option for sorting forum threads
                     <option value="comments">${_("by most activity")}</option>
                     ## Translators: This is a menu option for sorting forum threads