diff -up lftp-4.0.9/src/Http.cc.date_fmt lftp-4.0.9/src/Http.cc
--- lftp-4.0.9/src/Http.cc.date_fmt	2009-07-17 14:52:26.000000000 +0200
+++ lftp-4.0.9/src/Http.cc	2010-06-22 18:33:41.293950484 +0200
@@ -562,16 +562,10 @@ void Http::SendRequest(const char *conne
 		     (long long)((limit==FILE_END || limit>entity_size ? entity_size : limit)-1),
 		     (long long)entity_size);
       }
-      if(entity_date!=NO_DATE)
+      if(entity_date!=NO_DATE && entity_date>0L && entity_date<0xFFFFFFFF)
       {
 	 char d[256];
-	 static const char weekday_names[][4]={
-	    "Sun","Mon","Tue","Wed","Thu","Fri","Sat"
-	 };
-	 struct tm *t=gmtime(&entity_date);
-	 sprintf(d,"%s, %2d %s %04d %02d:%02d:%02d GMT",
-	    weekday_names[t->tm_wday],t->tm_mday,month_names[t->tm_mon],
-	    t->tm_year+1900,t->tm_hour,t->tm_min,t->tm_sec);
+	 strftime(d, sizeof(d), "%a, %d %b %H:%M:%S %Y GMT", gmtime(&entity_date));
 	 Send("Last-Modified: %s\r\n",d);
       }
       break;