ChangeLog               |    4 +++
 panel-plugin/datetime.c |   50 ++++++++++++++++++++++++++++++++++++++--------
 2 files changed, 45 insertions(+), 9 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 135d9cb..b62b5d9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2008-05-27  Diego Ongaro <ongardie@gmail.com>
+    * panel-plugin/datetime.c:
+      - Always update every second when seconds are shown (Bug #4117)
+
 2008-05-21  Diego Ongaro <ongardie@gmail.com>
     * panel-plugin/datetime.c:
       - Remove date input (Bug #4023)
diff --git a/panel-plugin/datetime.c b/panel-plugin/datetime.c
index 01c2542..1728e02 100644
--- a/panel-plugin/datetime.c
+++ b/panel-plugin/datetime.c
@@ -2,6 +2,7 @@
  *
  *  Copyright (C) 2003 Choe Hwanjin(krisna@kldp.org)
  *  Copyright (c) 2006 Remco den Breeje <remco@sx.mine.nu>
+ *  Copyright (c) 2008 Diego Ongaro <ongardie@gmail.com>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU Library General Public License as published
@@ -35,13 +36,14 @@
 #include "datetime.h"
 #include "datetime-dialog.h"
 
+#define DATETIME_MAX_STRLEN 256
 /*
  * Get date/time string
  */
 gchar * datetime_do_utf8strftime(const char *format, const struct tm *tm)
 {
   int len;
-  gchar buf[256];
+  gchar buf[DATETIME_MAX_STRLEN];
   gchar *utf8str = NULL;
 
   /* get formatted date/time */
@@ -57,6 +59,42 @@ gchar * datetime_do_utf8strftime(const char *format, const struct tm *tm)
   return utf8str;
 }
 
+/**
+ *  Check whether date/time format shows seconds
+ */
+static gboolean datetime_format_has_seconds(const gchar *format)
+{
+  static struct tm time_struct = {
+    .tm_sec   = 0,
+    .tm_min   = 0,
+    .tm_hour  = 0,
+    .tm_mday  = 1,
+    .tm_mon   = 0,
+    .tm_year  = 0,
+    .tm_wday  = 0,
+    .tm_yday  = 0,
+    .tm_isdst = 0
+  };
+  int len1;
+  int len2;
+  gchar buf1[DATETIME_MAX_STRLEN];
+  gchar buf2[DATETIME_MAX_STRLEN];
+
+  time_struct.tm_sec = 1;
+  len1 = strftime(buf1, sizeof(buf1)-1, format, &time_struct);
+  if (len1 == 0)
+    return FALSE;
+  buf1[len1] = '\0';
+
+  time_struct.tm_sec = 2;
+  len2 = strftime(buf2, sizeof(buf2)-1, format, &time_struct);
+  if (len2 == 0)
+    return FALSE;
+  buf2[len2] = '\0';
+
+  return len1 != len2 || strcmp(buf1, buf2) != 0;
+}
+
 /*
  * set date and time labels
  */
@@ -413,14 +451,8 @@ void datetime_apply_format(t_datetime *datetime,
     g_source_remove(datetime->timeout_id);
   }
 
-  if (strstr(datetime->date_format, "%S") != NULL ||
-      strstr(datetime->date_format, "%s") != NULL ||
-      strstr(datetime->date_format, "%r") != NULL ||
-      strstr(datetime->date_format, "%T") != NULL ||
-      strstr(datetime->time_format, "%S") != NULL ||
-      strstr(datetime->time_format, "%s") != NULL ||
-      strstr(datetime->time_format, "%r") != NULL ||
-      strstr(datetime->time_format, "%T") != NULL)
+  if (datetime_format_has_seconds(datetime->date_format) ||
+      datetime_format_has_seconds(datetime->time_format))
   {
     datetime->timeout_id = g_timeout_add(1000, datetime_update, datetime);
   }