diff -r a0946f209866 src/core/log.cc
--- a/src/core/log.cc	Mon Oct 20 13:31:25 2008 +0200
+++ b/src/core/log.cc	Mon Oct 20 14:03:30 2008 +0200
@@ -177,6 +177,10 @@
                   else if (lev == "prefix_time")
                     {
                       level |= LOG_PREFIX_TIME;
+                    }
+                  else if (lev == "prefix_time_s")
+                    {
+                      level |= LOG_PREFIX_TIME_S;
                     }
                   else if (lev == "level_error")
                     {
diff -r a0946f209866 src/core/log.h
--- a/src/core/log.h	Mon Oct 20 13:31:25 2008 +0200
+++ b/src/core/log.h	Mon Oct 20 14:03:30 2008 +0200
@@ -51,7 +51,8 @@
   LOG_LEVEL_ALL      = LOG_ALL,
 
   LOG_PREFIX_FUNC    = 0x80000000, // prefix all trace prints with function
-  LOG_PREFIX_TIME    = 0x40000000  // prefix all trace prints with simulation time
+  LOG_PREFIX_TIME    = 0x40000000, // prefix all trace prints with simulation time
+  LOG_PREFIX_TIME_S  = 0x20000000  // prefix all trace prints with simulation time (seconds)
 };
 
 /**
@@ -149,12 +150,20 @@
   static ns3::LogComponent g_log = ns3::LogComponent (name)
 
 #define NS_LOG_APPEND_TIME_PREFIX                               \
-  if (g_log.IsEnabled (ns3::LOG_PREFIX_TIME))                   \
+  if (g_log.IsEnabled (ns3::LOG_PREFIX_TIME) ||                 \
+      g_log.IsEnabled (ns3::LOG_PREFIX_TIME_S))                 \
     {                                                           \
       ns3::LogTimePrinter printer = ns3::LogGetTimePrinter ();  \
       if (printer != 0)                                         \
         {                                                       \
-          (*printer) (std::clog);                               \
+          if (g_log.IsEnabled (ns3::LOG_PREFIX_TIME_S))         \
+            {                                                   \
+              (*printer) (std::clog, true);                     \
+            }                                                   \
+          else if (g_log.IsEnabled (ns3::LOG_PREFIX_TIME))      \
+            {                                                   \
+              (*printer) (std::clog, false);                    \
+            }                                                   \
           std::clog << " ";                                     \
         }                                                       \
     }
@@ -319,7 +328,7 @@
  */
 void LogComponentPrintList (void);
 
-typedef void (*LogTimePrinter) (std::ostream &os);
+typedef void (*LogTimePrinter) (std::ostream &os, bool printSeconds);
 
 void LogSetTimePrinter (LogTimePrinter);
 LogTimePrinter LogGetTimePrinter(void);
diff -r a0946f209866 src/simulator/simulator.cc
--- a/src/simulator/simulator.cc	Mon Oct 20 13:31:25 2008 +0200
+++ b/src/simulator/simulator.cc	Mon Oct 20 14:03:30 2008 +0200
@@ -57,9 +57,16 @@
 // 
 
 static void
-TimePrinter (std::ostream &os)
+TimePrinter (std::ostream &os, bool printSeconds)
 {
-  os << Simulator::Now ();
+  if (printSeconds)
+    {
+      os << Simulator::Now ().GetSeconds () << "s";
+    }
+  else
+    {
+      os << Simulator::Now ();
+    }
 }
 
 #endif /* NS3_LOG_ENABLE */