diff --git a/ChangeLog b/ChangeLog
index 2980b23e6..aa1993e94 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,8 +1,8 @@
 2007-01-16  Tor Lillqvist  <tml@novell.com>
 
 	* glib/gthread.c (gettime): GetSystemTimeAsFileTime() returns 100s
-	of nanoseconds, so multiply by 100 to get nanoseconds which is
-	what we want.
+	of nanoseconds since 1601, so offset to Unix epoch (1970) and
+	multiply by 100 to get nanoseconds which is what we want.
 
 2007-01-15  Tor Lillqvist  <tml@novell.com>
 
diff --git a/glib/gthread.c b/glib/gthread.c
index 683ad4a47..116c2af25 100644
--- a/glib/gthread.c
+++ b/glib/gthread.c
@@ -554,7 +554,12 @@ gettime (void)
 #ifdef G_OS_WIN32
   guint64 v;
 
+  /* Returns 100s of nanoseconds since start of 1601 */
   GetSystemTimeAsFileTime ((FILETIME *)&v);
+
+  /* Offset to Unix epoch */
+  v -= G_GINT64_CONSTANT (116444736000000000);
+  /* Convert to nanoseconds */
   v *= 100;
 
   return v;
diff --git a/gthread/ChangeLog b/gthread/ChangeLog
index 82222eb80..f86b7fced 100644
--- a/gthread/ChangeLog
+++ b/gthread/ChangeLog
@@ -1,8 +1,9 @@
 2007-01-16  Tor Lillqvist  <tml@novell.com>
 
 	* gthread-win32.c (g_gettime_win32_impl):
-	GetSystemTimeAsFileTime() returns 100s of nanoseconds, so multiply
-	by 100 to get nanoseconds which is what we want.
+	GetSystemTimeAsFileTime() returns 100s of nanoseconds since 1601,
+	so offset to Unix epoch (1970) and multiply by 100 to get
+	nanoseconds which is what we want.
 
 2006-12-28  Tor Lillqvist  <tml@novell.com>
 
diff --git a/gthread/gthread-win32.c b/gthread/gthread-win32.c
index d55e265bb..78e2ecda4 100644
--- a/gthread/gthread-win32.c
+++ b/gthread/gthread-win32.c
@@ -550,7 +550,12 @@ g_gettime_win32_impl (void)
 {
   guint64 v;
 
+  /* Returns 100s of nanoseconds since start of 1601 */
   GetSystemTimeAsFileTime ((FILETIME *)&v);
+
+  /* Offset to Unix epoch */
+  v -= G_GINT64_CONSTANT (116444736000000000);
+  /* Convert to nanoseconds */
   v *= 100;
 
   return v;