diff --git a/dlls/ntdll/time.c b/dlls/ntdll/time.c
index c7546b1f78a..cd759018753 100644
--- a/dlls/ntdll/time.c
+++ b/dlls/ntdll/time.c
@@ -48,6 +48,16 @@
 
 WINE_DEFAULT_DEBUG_CHANNEL(ntdll);
 
+static CRITICAL_SECTION TIME_GetBias_section;
+static CRITICAL_SECTION_DEBUG critsect_debug =
+{
+    0, 0, &TIME_GetBias_section,
+    { &critsect_debug.ProcessLocksList, &critsect_debug.ProcessLocksList },
+      0, 0, { 0, (DWORD)(__FILE__ ": TIME_GetBias_section") }
+};
+static CRITICAL_SECTION TIME_GetBias_section = { &critsect_debug, -1, 0, 0, 0, 0 };
+
+
 #define SETTIME_MAX_ADJUST 120
 
 /* This structure is used to store strings that represent all of the time zones
@@ -481,11 +491,25 @@ BOOLEAN WINAPI RtlTimeFieldsToTime(
  */
 static int TIME_GetBias(time_t utc, int *pdaylight)
 {
-    struct tm *ptm = localtime(&utc);
-    *pdaylight = ptm->tm_isdst; /* daylight for local timezone */
-    ptm = gmtime(&utc);
-    ptm->tm_isdst = *pdaylight; /* use local daylight, not that of Greenwich */
-    return (int)(utc-mktime(ptm));
+    struct tm *ptm;
+    static time_t last_utc;
+    static int last_bias;
+    int ret;
+
+    RtlEnterCriticalSection( &TIME_GetBias_section );
+    if(utc == last_utc)
+        ret = last_bias;	
+    else
+    {
+        ptm = localtime(&utc);
+	*pdaylight = ptm->tm_isdst; /* daylight for local timezone */
+	ptm = gmtime(&utc);
+	ptm->tm_isdst = *pdaylight; /* use local daylight, not that of Greenwich */
+	last_utc = utc;
+	ret = last_bias = (int)(utc-mktime(ptm));
+    }
+    RtlLeaveCriticalSection( &TIME_GetBias_section );
+    return ret;
 }
 
 /******************************************************************************