diff -u trunk/panel-plugin/datetime.c exp3/panel-plugin/datetime.c
--- trunk/panel-plugin/datetime.c	2008-06-08 19:17:04.000000000 -0700
+++ exp3/panel-plugin/datetime.c	2008-06-12 11:24:50.000000000 -0700
@@ -51,6 +51,20 @@
 }
 
 /*
+ * Compute the wake interval,
+ * which is the time remaining from the current time
+ * to the next larger integral multiple of the update interval.
+ * Setting a timer to this value schedules the next update
+ * to occur on the next second or minute
+ * when the given update interval is 1000 or 60000 milliseconds, respectively.
+ */
+static inline guint datetime_wake_interval_from_current_time(const GTimeVal current_time,
+                                                             const guint update_interval_ms)
+{
+  return (update_interval_ms - datetime_gtimeval_to_ms(current_time) % update_interval_ms);
+}
+
+/*
  * Get date/time string
  */
 gchar * datetime_do_utf8strftime(const char *format, const struct tm *tm)
@@ -109,21 +123,15 @@
 }
 
 /*
- * set date and time labels
+ * set date and time labels when timer expires
  */
-gboolean datetime_update(t_datetime *datetime)
+static gboolean datetime_update1(t_datetime *datetime)
 {
   GTimeVal timeval;
   gchar *utf8str;
   struct tm *current;
   guint wake_interval;  /* milliseconds to next update */
 
-  /* stop timer */
-  if (datetime->timeout_id)
-  {
-    g_source_remove(datetime->timeout_id);
-  }
-
   g_get_current_time(&timeval);
   current = localtime((time_t *)&timeval.tv_sec);
 
@@ -143,31 +151,75 @@
     g_free(utf8str);
   }
 
-  /*
-   * Compute the time to the next update and start the timer.
-   * The wake interval is the time remaining
-   * to the next larger integral multiple of the update interval.
-   * Setting the timer to this value schedules the next update
-   * to occur on the next second or minute
-   * when the update interval is 1 or 60 seconds, respectively.
-   */
-  wake_interval = datetime->update_interval - datetime_gtimeval_to_ms(timeval) % datetime->update_interval;
-  datetime->timeout_id = g_timeout_add(wake_interval, (GSourceFunc) datetime_update, datetime);
+  /* Compute the time to the next update and start the timer. */
+  wake_interval = datetime_wake_interval_from_current_time(timeval, datetime->update_interval);
+  datetime->timeout_id = g_timeout_add(wake_interval, (GSourceFunc) datetime_update1, datetime);
 
-  return TRUE;
+  /* remove previous timer */
+  return FALSE;
 }
 
+/*
+ * set update intervals for the plugin and the tooltip
+ * start periodic updates
+ */
+void datetime_update(t_datetime *datetime)
+{
+  /* a custom date format could specify seconds */
+  gboolean date_has_seconds = datetime_format_has_seconds(datetime->date_format);
+  gboolean time_has_seconds = datetime_format_has_seconds(datetime->time_format);
+  gboolean has_seconds;
+
+  /* set update interval for the date/time displayed in the panel */
+  switch(datetime->layout)
+  {
+    case LAYOUT_DATE:
+      has_seconds = date_has_seconds;
+      break;
+    case LAYOUT_TIME:
+      has_seconds = time_has_seconds;
+      break;
+    default:
+      has_seconds = date_has_seconds || time_has_seconds;
+      break;
+  }
+  /* 1000 ms == 1 second; 60000 ms == 1 minute */
+  datetime->update_interval = has_seconds ? 1000 : 60000;
+
 #if USE_GTK_TOOLTIP_API
+  /* set update interval for the date/time displayed in the tooltip */
+  switch(datetime->layout)
+  {
+    case LAYOUT_DATE:
+      has_seconds = time_has_seconds;
+      break;
+    case LAYOUT_TIME:
+      has_seconds = date_has_seconds;
+      break;
+    default:
+      /* tooltips are disabled in this case, so set to a definite value */
+      has_seconds = FALSE;
+      break;
+  }
+  datetime->tooltip_update_interval = has_seconds ? 1000 : 60000;
+#endif
+
+  /* start periodic updates */
+  datetime_update1(datetime);
+}
+
+#if USE_GTK_TOOLTIP_API
+/*
+ * tooltip timer handler registered in datetime_query_tooltip()
+ */
 static gboolean datetime_tooltip_timer(t_datetime *datetime)
 {
-
-  /* flag to datetime_query_tooltip that there is no longer an active timeout */
+  /* The timer has expired, so datetime_query_tooltip() does not need to remove it. */
   datetime->tooltip_timeout_id = 0;
 
   /*
-   * Run datetime_query_tooltip if the mouse is still there.
-   * If it is run, it'll register *this* function to be called after another
-   * timeout. If not, *this* function won't run again.
+   * Trigger a "query-tooltip" event,
+   * which is handled by datetime_query_tooltip().
    */
   gtk_widget_trigger_tooltip_query(GTK_WIDGET(datetime->button));
 
@@ -175,6 +227,13 @@
   return FALSE;
 }
 
+/*
+ * "query-tooltip" event handler
+ * If tooltips are enabled,
+ * this handler is called when the cursor enters the plugin's button rectangle or
+ * the cursor moves while in the rectangle or
+ * indirectly by datetime_tooltip_timer() via gtk_widget_trigger_tooltip_query().
+ */
 static gboolean datetime_query_tooltip(GtkWidget *widget,
                                        gint x, gint y,
                                        gboolean keyboard_mode,
@@ -185,6 +244,16 @@
   struct tm *current;
   gchar *utf8str;
   gchar *format = NULL;
+  guint wake_interval;  /* milliseconds to next update */
+
+  DBG("enter");
+
+  /* stop timer */
+  if (datetime->tooltip_timeout_id != 0)
+  {
+    g_source_remove(datetime->tooltip_timeout_id);
+    datetime->tooltip_timeout_id = 0;
+  }
 
   switch(datetime->layout)
   {
@@ -195,6 +264,8 @@
       format = datetime->time_format;
       break;
     default:
+      /* Tooltips are disabled in this case, so it should not occur. */
+      DBG("tooltips are disabled");
       break;
   }
 
@@ -208,16 +279,10 @@
   gtk_tooltip_set_text(tooltip, utf8str);
   g_free(utf8str);
 
-  /* if there is no active timeout to update the tooltip, register one */
-  if (!datetime->tooltip_timeout_id)
-  {
-    /*
-     * I think we can afford to inefficiently poll every
-     * second while the user keeps the mouse here.
-     */
-    datetime->tooltip_timeout_id = g_timeout_add(1000,
-      (GSourceFunc) datetime_tooltip_timer, datetime);
-  }
+  /* Compute the time to the next update and start the timer. */
+  wake_interval = datetime_wake_interval_from_current_time(timeval, datetime->tooltip_update_interval);
+  datetime->tooltip_timeout_id = g_timeout_add(wake_interval,
+    (GSourceFunc) datetime_tooltip_timer, datetime);
 
   return TRUE;
 }
@@ -452,23 +517,12 @@
   }
 
 #if USE_GTK_TOOLTIP_API
-  /* update tooltip handler */
-  if (datetime->tooltip_handler_id)
-  {
-    g_signal_handler_disconnect(datetime->button,
-                                datetime->tooltip_handler_id);
-    datetime->tooltip_handler_id = 0;
-  }
   switch(datetime->layout)
   {
     case LAYOUT_DATE:
     case LAYOUT_TIME:
       gtk_widget_set_has_tooltip(GTK_WIDGET(datetime->button), TRUE);
-      datetime->tooltip_handler_id = g_signal_connect(datetime->button,
-                             "query-tooltip",
-                             G_CALLBACK(datetime_query_tooltip), datetime);
       break;
-
     default:
       gtk_widget_set_has_tooltip(GTK_WIDGET(datetime->button), FALSE);
   }
@@ -531,16 +585,6 @@
     g_free(datetime->time_format);
     datetime->time_format = g_strdup(time_format);
   }
-
-  if (datetime_format_has_seconds(datetime->date_format) ||
-      datetime_format_has_seconds(datetime->time_format))
-  {
-    datetime->update_interval = 1000; /* 1 second */
-  }
-  else
-  {
-    datetime->update_interval = 60000; /* 1 minute */
-  }
 }
 
 /*
@@ -658,6 +702,10 @@
   /* connect widget signals to functions */
   g_signal_connect(datetime->button, "button-press-event",
       G_CALLBACK(datetime_clicked), datetime);
+#if USE_GTK_TOOLTIP_API
+  g_signal_connect(datetime->button, "query-tooltip",
+      G_CALLBACK(datetime_query_tooltip), datetime);
+#endif
 }
 
 /*
@@ -693,8 +741,12 @@
 static void datetime_free(XfcePanelPlugin *plugin, t_datetime *datetime)
 {
   /* stop timeouts */
-  g_source_remove(datetime->timeout_id);
-  g_source_remove(datetime->tooltip_timeout_id);
+  if (datetime->timeout_id != 0)
+    g_source_remove(datetime->timeout_id);
+#if USE_GTK_TOOLTIP_API
+  if (datetime->tooltip_timeout_id != 0)
+    g_source_remove(datetime->tooltip_timeout_id);
+#endif
 
   /* destroy widget */
   gtk_widget_destroy(datetime->button);
diff -u trunk/panel-plugin/datetime.h exp3/panel-plugin/datetime.h
--- trunk/panel-plugin/datetime.h	2008-06-08 19:17:04.000000000 -0700
+++ exp3/panel-plugin/datetime.h	2008-06-12 10:13:32.000000000 -0700
@@ -46,11 +46,11 @@
   GtkWidget *vbox;
   GtkWidget *date_label;
   GtkWidget *time_label;
-  guint update_interval;  /* time between updates in milliseconds */
+  guint update_interval;          /* time between button updates in milliseconds */
   guint timeout_id;
 #if USE_GTK_TOOLTIP_API
+  guint tooltip_update_interval;  /* time between tooltip updates in milliseconds */
   guint tooltip_timeout_id;
-  gulong tooltip_handler_id;
 #endif
 
   /* settings */
@@ -82,7 +82,7 @@
   GtkWidget *cal;
 } t_datetime;
 
-gboolean
+void
 datetime_update(t_datetime *datetime);
 
 gchar *