diff -r ddec854843f1 Lib/datetime.py
--- a/Lib/datetime.py	Thu Sep 20 09:47:41 2012 +0300
+++ b/Lib/datetime.py	Thu Sep 20 15:16:28 2012 +0300
@@ -176,8 +176,9 @@
     freplace = None # the string to use for %f
     zreplace = None # the string to use for %z
     Zreplace = None # the string to use for %Z
+    sreplace = None # the string to use for %s
 
-    # Scan format for %z and %Z escapes, replacing as needed.
+    # Scan format for %z %Z %f and %s escapes, replacing as needed.
     newformat = []
     push = newformat.append
     i, n = 0, len(format)
@@ -218,6 +219,10 @@
                                 # strftime is going to have at this: escape %
                                 Zreplace = s.replace('%', '%%')
                     newformat.append(Zreplace)
+                elif ch == 's' and isinstance(object, datetime):
+                    if sreplace is None:
+                        sreplace = '%d' % object.timestamp()
+                    newformat.append(sreplace)
                 else:
                     push('%')
                     push(ch)
diff -r ddec854843f1 Lib/test/datetimetester.py
--- a/Lib/test/datetimetester.py	Thu Sep 20 09:47:41 2012 +0300
+++ b/Lib/test/datetimetester.py	Thu Sep 20 15:16:28 2012 +0300
@@ -1135,6 +1135,7 @@
         for fmt in ["m:%m d:%d y:%y",
                     "m:%m d:%d y:%y H:%H M:%M S:%S",
                     "%z %Z",
+                    "%s",
                     ]:
             self.assertEqual(dt.__format__(fmt), dt.strftime(fmt))
             self.assertEqual(a.__format__(fmt), dt.strftime(fmt))
@@ -1518,6 +1519,30 @@
         t = self.theclass(2005, 3, 2, 0, 0, 0, 0, MyTzInfo(3, 'name'))
         self.assertRaises(TypeError, t.strftime, '%Z')
 
+    # Run with US-style DST rules: DST begins 2 a.m. on second Sunday in
+    # March (M3.2.0) and ends 2 a.m. on first Sunday in November (M11.1.0).
+    @support.run_with_tz('EST+05EDT,M3.2.0,M11.1.0')
+    def test_strftime_naive(self):
+        t = self.theclass(1970, 1, 1)
+        self.assertEqual(t.strftime('%s'), '18000')
+        t = self.theclass(1970, 1, 1, 1, 2, 3, 4)
+        self.assertEqual(t.strftime('%s'),
+                        str(18000 + 3600 + 2*60 + 3))
+
+    def test_strftime_respect_timezone(self):
+        # Issue 12750: datetime.strftime('%s') should respect tzinfo
+        t = self.theclass(1970, 1, 1, tzinfo=timezone.utc)
+        self.assertEqual(t.strftime('%s'), '%d' % 0.0)
+
+        t = self.theclass(1970, 1, 1, 1, 2, 3, 4, tzinfo=timezone.utc)
+        self.assertEqual(t.strftime('%s'),
+                         '%d' % (3600 + 2*60 + 3 + 4*1e-6))
+
+        t = self.theclass(1970, 1, 1, 1, 2, 3, 4,
+                          tzinfo=timezone(timedelta(hours=-5), 'EST'))
+        self.assertEqual(t.strftime('%s'),
+                         '%d' % (18000 + 3600 + 2*60 + 3 + 4*1e-6))
+
     def test_bad_constructor_arguments(self):
         # bad years
         self.theclass(MINYEAR, 1, 1)  # no exception
diff -r ddec854843f1 Modules/_datetimemodule.c
--- a/Modules/_datetimemodule.c	Thu Sep 20 09:47:41 2012 +0300
+++ b/Modules/_datetimemodule.c	Thu Sep 20 15:16:28 2012 +0300
@@ -1120,6 +1120,13 @@
 }
 
 static PyObject *
+make_sreplacement(PyObject *object)
+{
+    _Py_IDENTIFIER(timestamp);
+    return PyObject_Str(PyNumber_Long(_PyObject_CallMethodId(object, &PyId_timestamp, "")));
+}
+
+static PyObject *
 make_freplacement(PyObject *object)
 {
     char freplacement[64];
@@ -1149,6 +1156,7 @@
     PyObject *zreplacement = NULL;      /* py string, replacement for %z */
     PyObject *Zreplacement = NULL;      /* py string, replacement for %Z */
     PyObject *freplacement = NULL;      /* py string, replacement for %f */
+    PyObject *sreplacement = NULL;      /* py string, replacement for %s */
 
     const char *pin;            /* pointer to next char in input format */
     Py_ssize_t flen;            /* length of input format */
@@ -1239,6 +1247,18 @@
             if (ptoappend == NULL)
                 goto Done;
         }
+        else if (ch == 's' && PyDateTime_Check(object)) {
+            /* format timestamp */
+            if (sreplacement == NULL) {
+                sreplacement = make_sreplacement(object);
+                if (sreplacement == NULL)
+                    goto Done;
+            }
+            assert(sreplacement != NULL);
+            assert(PyUnicode_Check(sreplacement));
+            ptoappend = _PyUnicode_AsStringAndSize(sreplacement,
+                                                  &ntoappend);
+        }
         else if (ch == 'f') {
             /* format microseconds */
             if (freplacement == NULL) {
@@ -4761,7 +4781,7 @@
     static char *keywords[] = {"tz", NULL};
 
     if (! PyArg_ParseTupleAndKeywords(args, kw, "|O:astimezone", keywords,
-				      &tzinfo))
+                                      &tzinfo))
         return NULL;
 
     if (check_tzinfo_subclass(tzinfo) == -1)