diff --git a/src/emqx_alarm_handler.erl b/src/emqx_alarm_handler.erl
index b57a04380..990f8a76e 100644
--- a/src/emqx_alarm_handler.erl
+++ b/src/emqx_alarm_handler.erl
@@ -105,7 +105,7 @@ init(_) ->
     {ok, []}.
 
 handle_event({set_alarm, {AlarmId, AlarmDesc = #alarm{timestamp = undefined}}}, State) ->
-    handle_event({set_alarm, {AlarmId, AlarmDesc#alarm{timestamp = erlang:system_time(second)}}}, State);
+    handle_event({set_alarm, {AlarmId, AlarmDesc#alarm{timestamp = erlang:system_time(millisecond)}}}, State);
 handle_event({set_alarm, Alarm = {AlarmId, AlarmDesc}}, State) ->
     ?LOG(warning, "New Alarm: ~p, Alarm Info: ~p", [AlarmId, AlarmDesc]),
     case encode_alarm(Alarm) of
@@ -199,5 +199,5 @@ clear_alarm_(Id) ->
 set_alarm_history(Id, Desc) ->
     His = #alarm_history{id = Id,
                          desc = Desc,
-                         clear_at = erlang:system_time(second)},
+                         clear_at = erlang:system_time(millisecond)},
     mnesia:dirty_write(?ALARM_HISTORY_TAB, His).
diff --git a/src/emqx_channel.erl b/src/emqx_channel.erl
index 4490ca40f..e1fd1b6f3 100644
--- a/src/emqx_channel.erl
+++ b/src/emqx_channel.erl
@@ -1345,7 +1345,7 @@ enrich_assigned_clientid(AckProps, #channel{conninfo   = ConnInfo,
 
 ensure_connected(Channel = #channel{conninfo = ConnInfo,
                                     clientinfo = ClientInfo}) ->
-    NConnInfo = ConnInfo#{connected_at => erlang:system_time(second)},
+    NConnInfo = ConnInfo#{connected_at => erlang:system_time(millisecond)},
     ok = run_hooks('client.connected', [ClientInfo, NConnInfo]),
     Channel#channel{conninfo   = NConnInfo,
                     conn_state = connected
@@ -1422,7 +1422,7 @@ parse_topic_filters(TopicFilters) ->
 
 ensure_disconnected(Reason, Channel = #channel{conninfo = ConnInfo,
                                                clientinfo = ClientInfo}) ->
-    NConnInfo = ConnInfo#{disconnected_at => erlang:system_time(second)},
+    NConnInfo = ConnInfo#{disconnected_at => erlang:system_time(millisecond)},
     ok = run_hooks('client.disconnected', [ClientInfo, Reason, NConnInfo]),
     Channel#channel{conninfo = NConnInfo, conn_state = disconnected}.
 
diff --git a/src/emqx_session.erl b/src/emqx_session.erl
index 2b03b7868..684589ff2 100644
--- a/src/emqx_session.erl
+++ b/src/emqx_session.erl
@@ -168,7 +168,7 @@ init(#{zone := Zone}, #{receive_maximum := MaxInflight}) ->
              awaiting_rel      = #{},
              max_awaiting_rel  = get_env(Zone, max_awaiting_rel, 100),
              await_rel_timeout = timer:seconds(get_env(Zone, await_rel_timeout, 300)),
-             created_at        = erlang:system_time(second)
+             created_at        = erlang:system_time(millisecond)
             }.
 
 %% @private init mq