diff -r 58eef400866e Doc/library/os.rst
--- a/Doc/library/os.rst	Sat Mar 03 16:20:37 2012 +0000
+++ b/Doc/library/os.rst	Sun Mar 04 00:59:33 2012 +0100
@@ -880,7 +880,9 @@ as internal buffering of data.
    Like :func:`utime` but if *path* is relative, it is taken as relative to *dirfd*.
    If *path* is relative and *dirfd* is the special value :data:`AT_FDCWD`, then *path*
    is interpreted relative to the current working directory.  *times* must be a
-   2-tuple of numbers, of the form ``(atime, mtime)``, or None.
+   2-tuple of numbers, of the form ``(atime, mtime)``, or None. atime and mtime
+   are :type:`int`, :type:`float` or a (sec, nsec) tuple where sec and nsec are
+   :type:`int` and nsec is in the range [0; 999999999].

    Availability: Unix.

@@ -920,8 +922,10 @@ as internal buffering of data.

    Set the access and modified time of the file specified by the file
    descriptor *fd* to the given values.  *atimes* must be a 2-tuple of numbers,
-   of the form ``(atime, mtime)``, or None.  If no second argument is used,
-   set the access and modified times to the current time.
+   of the form ``(atime, mtime)``, or None. atime and mtime are :type:`int`,
+   :type:`float` or a (sec, nsec) tuple where sec and nsec are :type:`int` and
+   nsec is in the range [0; 999999999]. If no second argument is used, set the
+   access and modified times to the current time.

    Availability: Unix.

@@ -1748,7 +1752,9 @@ Files and Directories

    Like :func:`utime`, but if *path* is a symbolic link, it is not
    dereferenced.  *times* must be a 2-tuple of numbers, of the form
-   ``(atime, mtime)``, or None.
+   ``(atime, mtime)``, or None. atime and mtime are :type:`int`, :type:`float`
+   or a (sec, nsec) tuple where sec and nsec are :type:`int` and nsec is in the
+   range [0; 999999999].


    Availability: Unix.
@@ -2195,7 +2201,10 @@ Files and Directories
    set to the current time. (The effect is similar to running the Unix program
    :program:`touch` on the path.)  Otherwise, *times* must be a 2-tuple of
    numbers, of the form ``(atime, mtime)`` which is used to set the access and
-   modified times, respectively. Whether a directory can be given for *path*
+   modified times, respectively. atime and mtime are :type:`int`, :type:`float`
+   or a (sec, nsec) tuple where sec and nsec are :type:`int` and nsec is in the
+   range [0; 999999999].
+   Whether a directory can be given for *path*
    depends on whether the operating system implements directories as files
    (for example, Windows does not).  Note that the exact times you set here may
    not be returned by a subsequent :func:`~os.stat` call, depending on the
@@ -2204,6 +2213,12 @@ Files and Directories

    Availability: Unix, Windows.

+   .. note::
+      To copy the access and modification time of a file with nanosecond
+      resolution, don't use :type:`int` on st_atime and st_mtime but
+      :func:`math.floor` to round correctly negative timestamps. See also
+      :func:`shutil.copystat`.
+

 .. function:: walk(top, topdown=True, onerror=None, followlinks=False)

diff -r 58eef400866e Lib/shutil.py
--- a/Lib/shutil.py	Sat Mar 03 16:20:37 2012 +0000
+++ b/Lib/shutil.py	Sun Mar 04 00:59:33 2012 +0100
@@ -4,13 +4,14 @@ XXX The functions here don't copy the re

 """

-import os
-import sys
-import stat
 from os.path import abspath
-import fnmatch
 import collections
 import errno
+import fnmatch
+import math
+import os
+import stat
+import sys
 import tarfile

 try:
@@ -154,7 +155,9 @@ def copystat(src, dst, symlinks=False):

     st = stat_func(src)
     mode = stat.S_IMODE(st.st_mode)
-    utime_func(dst, (st.st_atime, st.st_mtime))
+    atime = (math.floor(st.st_atime), st.st_atime_ns)
+    mtime = (math.floor(st.st_mtime), st.st_mtime_ns)
+    utime_func(dst, (atime, mtime))
     chmod_func(dst, mode)
     if hasattr(st, 'st_flags'):
         try:
diff -r 58eef400866e Modules/posixmodule.c
--- a/Modules/posixmodule.c	Sat Mar 03 16:20:37 2012 +0000
+++ b/Modules/posixmodule.c	Sun Mar 04 00:59:33 2012 +0100
@@ -3541,28 +3560,38 @@ posix_uname(PyObject *self, PyObject *no


 static int
-extract_time(PyObject *t, time_t* sec, long* nsec)
-{
-    time_t intval;
-    if (PyFloat_Check(t)) {
-        double d = PyFloat_AsDouble(t);
-        double mod;
-        *sec = (time_t)d;
-        mod = fmod(d, 1.0);
-        mod *= 1e9;
-        *nsec = (long)mod;
+extract_time(PyObject *obj, time_t* sec, long* nsec)
+{
+    PyObject *item;
+    long value;
+
+    if (PyTuple_Check(obj)) {
+        if (PyTuple_Size(obj) != 2
+            || !PyLong_Check(PyTuple_GET_ITEM(obj, 0))
+            || !PyLong_Check(PyTuple_GET_ITEM(obj, 1))) {
+            PyErr_SetString(PyExc_TypeError,
+                            "atime and mtime must be an int, a float "
+                            "or a tuple of 2 integers");
+            return -1;
+        }
+        item = PyTuple_GET_ITEM(obj, 0);
+        *sec = PyLong_AsTime_t(item);
+        if (*sec == (time_t)-1 && PyErr_Occurred())
+            return -1;
+        item = PyTuple_GET_ITEM(obj, 1);
+        value = PyLong_AsTime_t(item);
+        if (value == -1 && PyErr_Occurred())
+            return -1;
+        if (value < 0 || value > 999999999) {
+            PyErr_SetString(PyExc_ValueError,
+                            "nanosecond must be in range [0; 999999999]");
+            return -1;
+        }
+        *nsec = value;
         return 0;
     }
-#if SIZEOF_TIME_T > SIZEOF_LONG
-    intval = PyLong_AsUnsignedLongLongMask(t);
-#else
-    intval = PyLong_AsLong(t);
-#endif
-    if (intval == -1 && PyErr_Occurred())
-        return -1;
-    *sec = intval;
-    *nsec = 0;
-    return 0;
+    else
+        return _PyTime_ObjectToTimespec(obj, sec, nsec);
 }

 PyDoc_STRVAR(posix_utime__doc__,